140 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. [1885. 



delicate that I have been iiuable to detect them in any specimens pre- 

 served in alcohol. As soon as the young fish is expelled from the ovary 

 these processes rapidly diminish in size, and I have no doubt they 

 entirely disappear after a few hours. Their use is evidently to absorb 

 nourishment from the fluid in the ovary ; they also serve to aerate the 

 blood, for I have observed that on heating the fluid from the ovary, or 

 on mixing it with ether, there is an abundant escaj^e of gas. I think 

 these facts serve to explain the manner in which the fCBtus of the Em- 

 biotocoid fishes is nourished during its intra-ovarian development. 

 They have been frequently observed in the three varieties of this sort 

 of fish which are found in our waters." 



Within a very recent period, through the kind ofiBces of Miss Rosa 

 Smith, of San Diego, Cal., I have been enabled to obtain some well- 

 I)reserved material for purposes of study, which, while it enables me to 

 add considerably to our knowledge of the development of these singu- 

 lar fishes, also impels me to differ to some extent from the conclusions 

 of Dr. Blake. Miss Smith, at no little trouble to herself, obtained for 

 me gravid females of AmphisticJius arenatiis, JHtrema jacJcsoni, and Mi- 

 cromeirns aggregaius. Unfortunately this material, as well as some in 

 addition which I have obtained through the kindness of Dr. Bean from 

 the collections of the National Museum, rei)resents only the more ad- 

 vanced stages of foetal development, so that I am unable to add anj-- 

 thing to the very little which is known of the earliest stages of devel- 

 opment. Judging from the dates upon which the specimens collected 

 by Miss Smith were taken, it would seem probable that during the 

 months of October and November one would probably find the earlier 

 stages which are so desirable in order to clear up what must evidently 

 be a most interesting chapter in vertebrate embryology. 



The most striking characteristic of the fcetal surf-perches, as they lie 

 in the ovarian sac of the parent fish, is the exaggerated development 

 of the vertical or median fins, all of which combined present a lateral 

 area almost or quite as great as the united areas of the side of the 

 head, body, and tail. These fins present an exaggerated length and 

 height nowhere approached by the adults, and not exceeded in respect 

 to the width and relative length of the caudal fin by any fishes except 

 perhaps some of the domesticated Japanese breeds of Carassius, such 

 as the Kin-yi-ko. This extension of the area of the vertical fins is still 

 further increased by the production of the interradial membrane into 

 thin, highly vascular processes or marginal digitations. These Dr. 

 Blake has already described, but he has not mentioned the very extra- 

 ordinary waj^ in which these structures acquire their blood-supply, 

 which is, so far as I am aware, unique amongst young fishes, though 

 faintly approximated by the arrangement of the blood-supply seen in 

 the enormously developed translucent caudal of the Kin-yi-ko, as 1 have 

 had the opportunity to observe in the living fish. 



Description of the vascular supply of the yertical fins of Embiotocoid 



