FOURTEENTH ANNUAL MEETING. 65 



of itself. Not more than twenty or twenty-five individuals are 

 produced at one spawning. 



In another type. Anibleps, a form described by Professor Jeffries 

 Wyman, the yolk-sac itself is covered with villi, and, strange to 

 say, continues to grow for some time after the yolk has been ab- 

 sorbed, but the reason for this I am at a loss to understand. It 

 may, however, be that the function of the empty yolk-sac is in 

 this case somewhat similar to that of a placenta. 



The eggs of the surf perches of the west coast are developed 

 in membranous curtain-like folds of the upper wall of the ova- 

 rian sack. These membranes have a longitudinal direction, and 

 after the female is pregnant, and the embryos are somewhat ad- 

 vanced in development, they hang dowm between the embryos, 

 the latter being packed into the ovary somewhat like sardines in 

 a box. The peculiarity about the development of the young in 

 the ovary is that the vertical fins of the foetuses soon acquire an 

 exaggerated development and have a special set of blood vessels 

 sent to them, the fins also develop marginal prolongations which 

 become highly vascular, but afterward atrophy. This arrange- 

 ment, as well as the highly vascular skin of the foetuses, clearly 

 has relation to the respiration of the embryos while in the ovary. 

 Another peculiarity about this type is the enormous development 

 in the embryos of the back part of the intestine beyond anything I 

 have found in any other kind of fish embryos. This hypertrophy 

 of the intestine is of transient character, because this structure 

 afterward gradually diminishes in proportional size, and acquires 

 the relative proportion in respect to its diameter found in the 

 adult fishes in which there is no such an exaggerated develop- 

 ment of the intestine. The earlier writers, Girard and others, 

 who described these forms, mistook this projecting back part of 

 the intestine for a yolk bag. The fact, however, is, as we know 

 from the figures which are in existence, that this was not a true 

 yolk bag, but merely the intestine developed as I have de- 

 scribed it to you, with its terminal part thrust down and back- 

 ward, so as to project below the abdominal profile, somewhat 

 after the manner of a yolk bag. 

 Washington, D. C. 



