262 NEW YORK STATE MUSEUM 



side of the snout (plate 6, figure 5). In this stage a delicate mem- 

 brane, surrounding the embryo, separates it from the jellylike envelop. 



May 25th. The embryo shows but little advancement in this 

 period although it is possible that the specimen selected does not 

 represent the normal development. A slightly more pronounced 

 constriction back of the gill and arm region, an increase in the length 

 of the tail and some reduction of the yolk mass is evident (plate 6, 

 figure 6). 



May 27th. Buds of the gills and arms defined by lateral depres- 

 sions ; trunk and tail asstiming definite shape and yolk mass confined 

 to the region of the lower abdomen. Pigmentation increasing in 

 the eye areas and along the sides of the back and tail. 



Drawings of the foregoing stages are from preserved specimens; 

 those which follow were made from living embryos. 



June 2d. Length of embryo, 7.3 mm (plate 7, figure 2). 



The embryos in this stage are active and revolve freely on their 

 long axes within the gelatinous envelops. The pupils of the eyes 

 are developed; the gill and arm buds are of considerable size. In 

 the specimen figured there are three gill buds on the right side, 

 each separate, on the left but two and these coalesced. The gill 

 slits are still imperforate. Pigment distributed in small flecks on 

 the dorsum. 



June 4th. Length 9.4 mm (plate 7, figure 3). 



There is a marked development of the gills, the longest equal in 

 length to the head. The fringed condition of the fully developed 

 gills is here presaged by shallow scallopings of the margins. The 

 gill slits now perforate; circulation evident in the gills and along 

 the venter. Pigment spots coalescing more or less giving a decided 

 color pattern to the back and sides. Body behind the head com- 

 pressed; the posterior two-thirds of the trunk and tail distinctly 

 keeled above, the tail also keeled below. Arms half as long as the 

 head, legs indicated by slight swellings at the base of the tail. 



June 6th. Length 12.6 mm (plate 7, figure 4).. 



Gills fully developed, the fingers of the hand partly so. Legs 

 represented by mere swellings in the preceding stage, now ha,lf as 

 long as the arms and notched at their extremities. Of the total 

 length of the body, the tail occupies two-fifths. Trunk above keeled 

 almost to the head; the tail keeled above and to the origin of the 

 legs below. General color and pattern pickerel-like. The flecks of 

 yellowish green and orange pigment originating among those of light 

 and dark grey, by spreading and uniting give a mottled appearance 

 to the sides. On each side of the middle line of the back and tail 



