1885.] PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 131 



these markings iu the specimens which I examined ; but, when iihiced 

 under the microscope, were found to form a peculiar structure, which 

 possibly may have some connection with the process of nutrition in their 

 peculiar mode of gestation. 



" The sac itself seemed nearly homogeneous in structure, but the striae 

 are made up of spherical, or in some cases pyriform or cylindrical, 

 papillae or villi, projecting from the surface and arranged so nearly 

 together in a linear series as to give the appearance of a continuous 

 band. In regard to the minute structure of these pai^illae, as far as it 

 could be determined from an alcoholic specimen, they consist externally 

 of an exceedingly thin membrane, inclosing a vast number of minute 

 granules; no vessels were seen in connection with them nor in the mem- 

 brane to which they were attached. There was no appearance of any 

 communication between the cavity of the papilla and that of the mem- 

 brane to which it was attached. Within the latter, but more nearly in 

 contact with the intestines, there was a second more delicate membrane, 

 which seemed to be a continuation of the parietal peritoneum. No 

 traces of the yelk were found iu connection with the intestines. 



" III. The third specimen is much longer and measures 10 inches in 

 length ; the ovary had been ruptured, so that some of the foetuses had 

 escaped into the cavity of the abdomen, but the whole number of young 

 taken from the parent was much greater than iu the preceding case, 

 namely, eighteen ; one of these was projecting from the ge^iital opening. 

 The}^ generally resembled the preceding except in size, though the eyes 

 had become more prominent, and the iris now exhibited its lateral pro- 

 jections sufficiently developed to give the pupil the shape of a dumb- 

 bell. The umbilical sac has become much larger than in the embryos 

 first described, and measures three-eighths of an inch in diameter. The 

 papillte of the yelk-sac are much more distinct, and contain colored 

 granules. The yelk-sac communicates with the cavity of the abdomen 

 by a long fissure extending from a point just behind the union of the 

 opercula nearly as far as the anal opening, consequently beyond the ven- 

 tral fins. It is from the circumstance just mentioned, doubtless, that 

 an explanation is to be found of the non-union of the ventrals in the 

 adult. The scales terminate abruptly at the edge of the fissure. The 

 intestine, as in the first described embryos, were invested by the internal 

 sac, which was regarded as parietal peritoneum. No bands were visible 

 on the flanks of the body, nor were the anal fins yet modified to mark 

 the sexes. A rudimentary liver is visible in these specimens, extending 

 backwards on the left side of the intestinal mass. The intestinal canal 

 is of almost uuiibrm size throughout,^ there being no distinction between 

 intestine and stomach. 



" IV. This specimen measured a little less than 10 inches in length, but 

 the embryos were of much larger size, having a length of 2^ inches ; 

 the umbilical sac had disappeared, but the fissure on the under side of 

 the abdomen still remained, and, what seems quite remarkable, had 

 grown in dimensions just in proportion to the entire foetus, so that in 



