234 JOHNS HOPKINS UNIVERSITY MORPHOLOGICAL MONOGRAPHS. 



sexually immature ascidiozooids, and an indefinite series of sexual 

 hermaphrodite ascidizooids. 



In salpa, the first generation, or solitary salpa, has enormously 

 enlarged its capacity for budding, so that it is able to mature from fifty 

 to two hundred buds at one time, and to produce many hundreds during 

 its life. The second generation has lost all power to bud, so that the life- 

 cycle has become limited to two generations. 



The solitary salpa produces ovarian eggs, and, like its ancestors and 

 like pyrosoma, passes them into the buds to mature and ripen and 

 develop. As the aggregated salpse do not bud, they have lost their 

 ancestral ovaries, and all the female germ cells now remain in the body 

 of the solitary salpa at the base of the stolon and form its ovary, as 

 they formed the ovary of the primitive tunicate from which tJie method of 

 budding has been inherited. The testis of the solitary salpa remains 

 embryonic, its cells multiply by karyokinesis and grow out into the 

 stolon, and give rise to the testes of the chain-salpae, which, however, 

 contain no female germ cells and produce no eggs. 



Seeliger holds, indeed, that we must not compare in this way the 

 whole life-history of salpa with the whole life-history of pyrosoma, but 

 that we must neglect the history of the formation of the four primary 

 ascidiozooids by budding from the body of the cyathezooid, and of the 

 first generation of secondary ascidiozooids from the bodies of the primary 

 ascidiozooids, and that we must compare the budding of salpa with the 

 budding of the secondary ascidiozooids ; but as the evolution of the life- 

 history of salpa out of a dislocated fragment in the life-cycle of pyro- 

 soma is not proved by any evidence, it is surely more rational to regard 

 both life-histories as divergent modifications of a common ancestral life- 

 history. 



