552 KECOED OF CURRENT RESEARCHES RELATING TO 



observed them, Mr. W. K. Brooks, of America, these organs are 

 developed from the remarkable aggregation of cells, which, as contain- 

 ing fat in large quantities, has been called the elceohlast, found at the 

 hinder end of the so-called foetal or solitary form. With this view 

 Professor Salensky disagrees ; by the older, and indeed by the 

 majority of naturalists, it has been held that the testes are developed 

 at a later period than the ovary ; in an early stage of the development 

 of the " chain-Salpse " there is found at the hinder end of the body an 

 aggregation of cells ; later on this commences and continues to grow 

 forward, and, investing the hind-gut, forms a testicular layer, from 

 the lateral portions of which the testes are developed, while its 

 superior and inferior portions take no part in the formation of the 

 testes, and in all probability disappear altogether. According to 

 Professor Salensky's observations this organ has no relation to the 

 claeoblast, as Brooks supposed that it had. What relation has this 

 mode of development to the question of alternate generations? And, 

 firstly, as to one striking peculiarity, which is this : the ova of the 

 chain- SalpfB attain a comparatively high degree of development before 

 the chain breaks free from the mother. This is an arrangement 

 altogether unlike that which obtains in other forms that present this 

 method of generation, and has led to the view that the solitary Salpos 

 are females, but that their ova are developed in the chained forms 

 to which they give rise. 



The chained forms are, according to this view, males, and the 

 part homologous to the elasoblast is that which gives rise to the 

 testes ; but as Salensky does not regard this view of the origin of 

 the ovaries as correct, and believes that he has shown that the testes 

 have no homologous relation to the elfeoblast, it follows that he looks 

 upon the generation of these forms as being truly of the alternate 

 mode. 



On comparing these Salpce with allied forms, a very great 

 similarity is found to obtain between them and Pyrosoma ; in this 

 latter the ovum gives rise to a " cyathozooid " (Huxley) ; this 

 develops by gemmation from its " stolo prolifer " the ascidiozoids, 

 which are, like all Ascidice, hermaphrodite; the mother-form or 

 " nurse " gives rise to an ovarian tube, which passes into the daughter- 

 forms, and there produces ova ; the only difference between them lies 

 in the fact that Pyrosoma first gives rise to four ascidiozoids only, 

 and that these undergo further gemmation ; in the Salpce there is 

 nothing that is analogous to this. 



Leaving the other forms of which the author treats, and merely 

 indicating that he regards the aggregation of cells found in the tail 

 of DoUohim as intermediate between the chorda of the Ascidian larva 

 and the elaeoblast of the Salpce, we would note that he considers this 

 last-mentioned organ as being obviously of greater morphological 

 importance than a mere store of nutrient material, and as being 

 provisional only ; if this view be just, there is no obstacle to prevent 

 our regarding the solitary form of Salpce as exactly similar to the 

 "nurse-form" of Doliolmn, and, speaking more generally, we iind 

 that the " nurse " of the Salpce corresj)onds to the larvae of other 



