THE HEMIMYARIA (SALPIDAE). 415 



points, such as the cleavage, the formation of the germ-layers and the 

 development of the placenta, the recorded investigations are incom- 

 plete and contradictory, and we have statements which we must 

 hesitate to accept because they are at variance with all that is known 

 of the development of other Tunicates (and of animals in general). 

 In our account we shall have these difficulties to contend with 

 and must restrict ourselves to giving a brief survey of what at the 

 present time seems to lie fairly well established. We cannot enter 

 upon the many contradictory and obscure points in connection with 

 this subject. 



Among the Salpidae, the sexual individuals (the forms belonging 

 to the chain) are hermaphrodite, but the time of maturation of the 

 male and female products differs. The individuals of the young 

 chain set free from the stolon of the "nurse" generation (solitary 



• / 



Fig. 206. — Side-view of Salpa demooratica-mucronata (combined after Claus and 

 Salbnskt). '/. atrial cavity; e, atrial aperture; end, endostyle ;/, peripharyngeal 

 band; i, branchial aperture ; k, gill; /*, nerve-ganglion ; /"/, nucleus; od, oviducl , 

 ov, ovary (consisting of a single egg-follicle) ; ph, pharyngeal cavity ; x, aperture of 

 the oviduct. 



form) are at first female ; they are fertilised by the individuals of 

 another chain, and each develops one embryo. Only as this develops, 

 do the testes become functional. 



The Sal pidae, as a rule, develop only one egg. The whole ovary 

 ( Fig. 206, ov) consists, in such cases, of a single follicle which con- 

 tains the egg and is connected with the epithelium of the atrial 

 cavity * by a strand-like oviduct in which two portions can be dis- 



* [Owing to the peculiar relations existing between the pharynx and the 

 atrial cavity in Salpa, it becomes extremely difficult to decide their limits ; 

 the term respiratory cavity (Ath.emb.dhle) is commonly loosely applied to the 

 greater part of this chamber. We have, however, thought it advisable to drop 

 this word and to use in its stead the more specific terms atrial cavity and 

 pharyngeal cavity in those cases in which we were able to determine the 

 portion of the general cavity which was being referred to. — Ed.] 



