32 SIDNEY P. HARMER. 



the description of Uljaniti (35), a sei'ies of buds in which 

 there is a very small amount of differentiation. These " Ur- 

 knospen " consist of a layer of ectoderm surrounding a mass of 

 embryonic cells which are but slightly differentiated (1. c, pi. 

 X, fig. 3). These buds divide up into numerous similarly- 

 constituted buds, so that the sexual individual of Doliolum 

 takes its origin from a group of cells which is very similar to 

 the young " secondary embryos " of Crisia. 



The same method of reproduction characterises the remark- 

 able Dolohinia, recently described by Korotneff (22). This 

 animal is closely allied to Doliolum, if, indeed, it should not 

 be placed in that genus. The only phase in its life-history 

 which is so far known is a gelatinous axis, bearing very nume- 

 rous Doliolum-like zooids, and which probably corresponds 

 to the dorsal process of Doliolum. The axis bears numerous 

 buds, wandering about on its surface by means of pseudo- 

 podia. The buds have probably been derived from the seg- 

 mentation of the ventral stolon of an asexual form. They 

 increase in number by division. Should one of the daughter- 

 buds fix itself on the base of a young zooid, it becomes a 

 bean-shaped body, which gives rise to a large number (as 

 many as forty) of new buds. The young buds, at the stage at 

 which they become free, consist of a solid mass of cells in 

 which a very small amount of differentiation has taken place. 



The formation of the secondary buds, as shown in Korot- 

 ueff's pi. xiii, figs. 14, 15, has thus a striking resemblance to 

 the mode of development of the secondary embryos in Crisia; 

 neglecting the not unimportant difference that in the former 

 case the budding organ is itself a bud, and in the latter case 

 an embryo. 



A similar process probably takes place in Anchinia (21) ; 

 and Uljanin (1. c, pp. 106 — 117) brings forward evidence to 

 show that the same is true of some of the compound Asci- 

 dians. The larva of Distaplia magnilarva, for instance, 

 gives rise to structures comparable with the " Urknospen " of 

 Doliolum. Uljanin comes to the conclusion that the bud- 

 ding of adult Tunicates is derivable from a division of " very 



