The live males were removed from under the lobes of the abdomens of the females (one male in each female, and always on the same spot) and placed on paper wetted with salt water, where they slowly walked about in a sideways direction. The females moved their legs to and fro, and contracted their abdomen only on touching the ventral appendages. They kept rapidly paddling with their gill-like cephalic appendages as mentioned above. I presume that the male and female get their necessary aëration through the motions of the gills of the prawn, and as the embryos are laterally covered by the marsupial lobes of the females, and exteriorly by the carapace of the prawn, the additional fanning of the female cephalic appendages is intended for aërating eggs or the embryos only. The functions of the gills in the carapace of the prawn infected with the Bopyrus, are undoubtedly impaired through the presence of the latter, thus shortening the life of the former; the lessened aëration conditions but one brood of the Bopyrus; both adults of the latter gradually die off in ratio with the prawn.2 The embryos after quitting their larval skin, FIG. 2.-Bopyrus palamoneticola Pack., much enlarged. (From Scient. Amer., Sept. 3, 1881). 4, female Bopyrus, dorsal view; B,ventral view of same, C, dorsal view of male; D, male, side view; (B) c, eggs; m, male. 'This is also the case with Cymothoa, according to Professor J. C. Schiödte in Annals Mag. Nat. History, Ser. v, Vol. 2, 1878, p. 195. On the Propagation and Metamorphosis of the suctorial Crustacea of the family Cymothoida. The suggestion that the Bopyrus and its host die "in ratio" together, was supported by several experiments, by placing separately about half a dozen of both infected and healthy prawns into quart jars full of marine water, wherein in every instance the infected prawns died several hours before the non-infected ones. are, what Bate and Westwood have already hinted at, in their highest and most advanced stage; the organs of sense and motion being proportionately larger and better developed at that period of their existence than ever after. In this free stage the young get their aëration through the entire integument. I suppose that after the brood of larvæ have left the marsupium of the female, they will actively swim about in the sea, attaching themselves, if possible, to egg-clusters of female prawns; with the young of the latter they simultaneously grow up, and enter their branchial cavity in pairs at an early period of life. In June, 1881, I found a few (out of several hundred) live females with males, the former with empty marsupia, which fact led me to believe that this Bopyrus may produce more than one brood, but the few cases may either be exceptions or, what is more likely, the broods had just left their marsupia, leaving the parents to their fate. The following observations were made on the eggs and embryos taken from the marsupium of live female specimens. The specimens were obtained during May, June and July this year (1881), and the number of more advanced developmental stages was not at all augmented in the latter month, nor was this the case with a lot received late in August. By far the greater number of prawns, regardless of sex,2 exhibited through their transparent carapace the yellowish eggs of the female Bopyrus, nearly all, with but a few exceptions, showing under the microscope the peripheric blastoderm cells within which a larger or smaller, entire or subdivided yolk-mass could be distinguished (see Pl. 1, fig. 1). The few exceptions just mentioned showed, when viewed from the side, the budding limbs and segments very indistinctly, the two body-ends however, head and tail (pleon) being more distinct, exhibiting the form seen in Pl. 1, fig. 3. Those prawns which showed through their swollen carapace a more grayish mass, contained the Bopyrus embryos invariably in their larval skin, a drawing of which is seen in Pl. 1, fig. 2. These embryos contained a central undifferentiated yolk-mass, with a few yellow oil-globules and some larger orange-colored 1 Bate and Westwood, p. 217. Dr. Heinrich Rathke (I quote from Bate and Westwood, p. 217) found the female Bopyri upon female prawns, of which he had observed several hundreds thus infected, whilst quite as many male prawns were found to be free from their attacks. pigment masses, the latter being nearer the dorsal line. It must be understood that the embryo in Isopod crustaceans is bent backward, head and tail nearly touching each other, the limbs, on the other hand, being in the peripheric layer. In Fig. 4 an embryo is shown freed from the egg-skin or chorion, thereby turned into its opposite direction, concave ventral and convex dorsal side. A pereiopod or thoracic leg; the end of the abdomen (telson) with the last pair of legs (uropods), a pleopod, one of the second pair of antennæ with dd— ? remnants of earlier embryonic bristles are shown respectively in Figs. 4, 4a, 4b, 4c, and 4d. By working with the dissecting needles, the embryo (in Fig. 4 freed from the chorion, but still enclosed in its larval skin) with some difficulty could also be freed, limb after limb, from its larval skin (amnion), then appearing as in the much enlarged Fig. 5. This, as has already been said, is the highest and most advanced stage of the Bopyrus, which, under favorable circumstances, will enter the gill-cavity of the earlier developmental stages of the prawn, where it, as the prawn advances, will, when a female, lose its eyes, both antennæ, the uropods, etc.; while the pleopods will deform into the abdominal lobes and from the seventh free segment will bud a pair of legs. But if a male, where does the eighth pair of thoracic legs originate from? From the first pair of pleopods? I should rather infer that the pair of uropods will yield the eighth pair of legs in the male. The fact that the male has no abdominal appendages (so-called gills of the female) gives strength to the assumption that the eighth pair of legs in the male are derived from one pair of the pleopods, since the former (female) have the same origin. EXPLANATION OF PLATE I. FIG. 1.-Egg after segmentation. a. Blastoderm-cells. b. Subdivided central yolk ball. FIG. 2. Later stage. Lateral view. c. Head. a. Chorion. b. Larval skin-amnion. aa. Mandibles. bb. Maxilla. 1. Antennula. II. Labrum. III. Antenna. IV. Maxilla? y. Yolk with orange pigment balls. XI. Seventh free thoracic segment. o. Twelfth to sixteenth segment (abdominal segments, pleopods concealed). t. Telson, uropods covered beneath the dorsal bent. FIG. 3.-Profile view of embryo; dorso-ventral. a. Head. b. Pleon. FIG. 4.-Older embryo in larval skin. Lateral view. FIG. 4 a.-Telson or fourteenth segment with the uropods of Fig. 4 in larval skin. Highly magnified. Showing pigment. FIG. 46. One of the pereiopods of larva (Fig. 4) in larval skin. FIG. 6. Stellar form of pigment of adult male; from dorsal side. FIG. 7.-Leg of adult male Bopyrus. FIG. 8.-Antenna of male B. magnified 500 X. FIG. 9.—One of the maxillæ with palpus of the female. arthr. Original joint. mn. Muscle-nerves. p. Dentritic pigmentation. 1. Maxillary palpus with nine tentacles. 7. Disconnected part (from the other half). B. Anterior free lobe. FIG. 10. First thoracic lobe of female. p. Pigment. t. Tentacles. FIG. 11.-Outline of one of the abdominal appendages (gills) of female. 7. Smaller, thicker lobe, put aside. FIG. 12.-Schematic figure showing position of the two maxillæ underneath the cephalon. IN THE HETEROGONY OF OXALIS VIOLACEA. BY WILLIAM TRELEASE. May of the present year, after collecting specimens of the violet wood-sorrel about Madison, Wis., I noticed that I had succeeded in getting two well-marked forms of flowers, in one of which the pistils were considerably longer than the stamens, which were in two sets of slightly different length, while in the other the pistils were shorter than either set of stamens. On the supposition that these were respectively the long-styled and short-styled forms of a trimorphic species, careful search was made for the mid-styled form. In a class exercise in analysis, something over one hundred plants were studied, but only the two forms above mentioned were found, and in nearly equal num FIG. 1.—Long-styled flower of Oxalis violacea. FIG. 2.-Short-styled flower of the same species. Magnified eight dianieters. bers. An examination, made by myself, of the flowers of about a hundred additional plants, from different localities within an area of a few miles, gave a similar result. Up to this time no accurate record of the number of plants of either form, or of the absolute lengths of stamens and pistils had been made, attention having been given only to the presence or absence of mid-styled flowers, and, in a general way, to the relative abundance of the two forms which were found. After this eightyone flowers, gathered at random from as many plants, were carefully examined, and it was found that in fifty-one the styles were nearly twice as long as the average of both sets of stamens, while the styles of the remaining thirty were shorter than either |