98 



Annals of the Carnegie Museum. 



there are as many as five. In Cnesterodon there are none. In Phal- 

 lotorynus there are three, the first and last are long and needle-like 

 a-nd the central one is expanded or club-shaped at the tip. Just before 

 these there is a single short sta^'. Garman {h, Plate VIII) has figured 

 many of the different species. The muscular mass enveloping the 

 base of the anal is directly attached by a tough ligament to the 

 vertebral column. 



Fig. I. Diagrammatic sketch of Pcecilia vivipara, cf , showing modification of 

 last two precaudal vertebrge to form a support for the intromittent organ, i, 

 intestine; I, liver; t, testicle; abl, air-bladder; ii, ureter; ctr, ends of ribs cut off 

 to show abdominal cavity. 



For the modified subvertebral processes Philippi {d. 1908) has pro- 

 posed the term ' gottapophysis.' In Pcecilia vivipara (Fig. i) the first 

 •of these processes joins directly with the enlarged first interha?mal. 

 The other interhsemals or radialia, with which the rays of the anal fin 

 are articulated, are sharp and slender, and all, including the first en- 

 larged one, are enclosed in the mass of muscles, which controls the 

 movements of the fin. 



The forward position of the anal fin in the male causes the crowding 

 of the viscera into the extreme forward end of the body-cavity. In 

 females the development of young within the ovarial sack likewise 

 causes a pushing of the viscera toward the head. In this sex the air 

 bladder is a simple oval sack, but in males the development of the sub- 

 vertebral stays causes a split in the organ, so that posteriorly it is 

 bilobed, with the subvertebral processes occupying a position between 

 the lobes. 



Breeding Habits. 



The act of copulation in the viviparous Poeciliids has not often been 

 seen. Agassiz (1853, p. 135) witnessed it in Mollienisia latipimia, 

 and in this manner learned that the two forms, which had previously 



