904 FISHES — CYPBINODONTID^. 



Fundulus, and different in appearance, so that we feel reluctant to nnite the two gen' 

 era, althoagh the technical difierences are very alight. ' Species all American. Surface- 

 swimmers, feeding upon insects. 



The species are qnite nnmerons, but have been little studied. 



The following article from the pen of John A. Ryder, on the develop- 

 ment of a species of this genus is almost the only attempt at the study 

 of the breeding peculiarities of the Cyprinodonts : 



" Since we have taken up our temporary residence at Cherrystone, Virginia, we have 

 found this interesting genus of cyprinodonts in great abundance in fresh and brackish 

 water streams, also in a fresh water pond in the vicinity, a few miles south of where 

 our station is located. In the latter situation three forms have been collected, all of 

 which are in breeding condition — we will not say spawning condition, as they do not, as 

 do most other fishes, commit their ova to the care of the element in which they live, 

 but carry them about in the ovary, where they are impregnated and where they develop- 

 in a very remarkable manner. 



"Of the manner of impregnation we know little or nothing, except the evidence 

 furnished by the conformation of the external genitalia of the two sexes. In the adult, 

 male, which measures one and one-eighth of an inch in length, the anal fin is strangely 

 modified into an intromittent organ for the conveyance of the milt into the ovary of 

 the female ; a tubular organ appears to be formed by the three foremost anal rays, but 

 one which is greatly prolonged and united by a membrane. At the apex these rays are 

 somewhat curved toward each other, and thus form a blunt point, but the foremost one 

 of the three rays is armed for its whole length with ridges at its base and with sharp 

 recurved hooks at its tip, the other two at their tips similarly with hooks, and between 

 their tips are two small fenestra or openings which possibly communicate directly with 

 the sperm ducts from the testes. The basal elements of the fins are aggregated into a 

 cylindrical columnar truncated bony mass, which is prolonged upward into the cavity 

 of the air-bladder for the distance of nearly the eighth of an inch ; from it a series of 

 fibrous bands pass to the dorsal and posterior wall of the air-bladder to be inserted in 

 the median line. Whether this bony column serves to steady the fin in the act of copu- 

 lation, or whether it serves to give passage to the sperm duct, is an unsettled question 

 with the writer. The modified anal fin of the main measures a third of an inch in 

 length. Other peculiarities of the male are noticeable — for instance, the more ab- 

 breviated air-bladder or space which also occupies a more oblique position than in the 

 female. The most remarkable difference presented by the male as compared with the 

 female, however, is his inconsiderable weight, which is only 160 milligrames, while that 

 of the gravid female is 1,030 milligrames or nearly six and one-half times the weight of 

 the male. 



" The female, as already stated, is larger than the male, and measures one inch and 

 three-fourths in length. The liver lies for the most part on the left side. The intestine 

 makes one turn upon itself in the fore part of the body cavity and passes back along the 

 floor of the abdomen to the vent. The air-bladder occupies two-fifths of the abdominal 

 cavity, and at its posterior end the wolffian duct traverses it vertically, to be enlarged 

 near the outlet into a fusiform urinary bladder of very much the same form as in many 

 embryo fishes, as demonstrated by Professor Kupflfer and myself. The ovary is a simple, 

 impaired organ which lies somewhat to the right and extends from the anterior portion 

 of the body cavity to the hinder end, and serves to fill up its lower moiety when fnlly 

 developed. The ova, when full grown, are each enveloped in a sac or follicle supplied 



