1885.] PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 155 



VI. — Habits of Gambusia during the breeding season. 



Mr. A. A. Duly has informed me that he lias witnessed the act of copu- 

 lation and the birth of the young of Gambusia. In coitus the male's head 

 is turned in the direction of the tail of the female, the prolonged anal fin 

 seeming to be thrust into the external opening of the ovarian duct or 

 genital pore of the female, which lies just in advance of the anal tin. 



The young when born are stated by Mr. Duly to be about three- 

 eighths of an inch in length, and to be expelled in a single mass, con- 

 sisting of eight to eleven young fishes at a single effort. This mass as 

 soon as it escapes is seen to be composed of the infant Gambusias, which 

 at once separate and swim away. No membranes seemed to be expelled 

 together with the mass of young, so that it is probable that in this species 

 as in Anahleps and the Embiotocidcv the foetuses rupture the follicles in 

 which they were developed a short time before birth. I say a short time 

 before birth, because our observations indicate that, unlike Anahleps and 

 3licr()metrus, the development of Gumhusia is essentially completed 

 within the follicles, and no yelksac remains outwardly visible when 

 the young are set free. 



My informant also tells me that the parent fishes devoured their 

 young as soon as they were born if they were not separated, by trans- 

 ferring one or the other at once to another aquarium. Fright seemed 

 to hasten or precipitate the parturition, which Mr. Duly tells me actually 

 took place under such circumstances. He also noticed that more than 

 one brood seemed to be produced by the same parent consecutively 

 and during the same season, and he has reason to think that more may 

 have been produced, as his observations only extended over the latter 

 part of summer with adults brought from Cherrystone, in August and 

 September, which he kept in aquaria in the National Museum. 



VII. — The VIVIPARITY of Fundulus. 



On Plate XI, Figs. 29 and 30, I figure two views of another type of 

 Cyprinodont embryos, viz, Fundulus majalis, also obtained at Cherry- 

 stone, Va., July 18, 1881. In this case a well-marked zona w^as de- 

 veloped investing the developing embryo. The oil drops were super- 

 ficially embedded in the yelk the same as in Gambusia. A great net- 

 work of vessels surrounded the yelk, as may be seen in both figures; 

 these spread over the yelk from the two Cuvierian veins which pass 

 out from the side of the body of the embryo just in front of the pectoral 

 fin folds, and are gathered inferiorly, as represented in Fig. 30, into a 

 great median vein which is extended from the venous end of the heart. 



A hood is probably formed at the sides of the head of this species the 

 same as in Gambusia^ as indicated by the vascular membrane at the 

 sides of the head raised from contact w-ith the yelk, as shown in Fig. 30. 



The body cavitj under the axis of the embryo is a deep oval sinus 

 extending down a little distance into the substance of the yelk, as showi^ 

 in Fig 29, behind the rudiments of the pectoral fliis. 



