NoTT. — On N.Z. Composite Asciclians. 329 



common ground furnished by their connection, making the 

 spirally-coiHng vas deferens, presence of stellate spicules, and 

 double form of the body the chief characteristics of the new 

 group. This arrangement certainly commends itself more 

 than the former would do ; but the family Diplosomidae would 

 still be a difficulty, though separated readily by the straight 

 course of its vas deferens. Moreover, the corm in Herdman's 

 family is so highly specialised that it seems quite impossible 

 to unite it with the Didemnidae. 



A third course is open — that, namely, of enlarging the 

 borders of some one family so as to include the new genus. 

 Now, to unite Polysyncraton with Coelocormus would be open 

 to the objection urged above. To unite it to the genera placed 

 under the DiplosomidEe would tend to confuse that family with 

 the Didemnidee ; and to unite it with the Didemnidae would 

 destroy the distinctness of that group, as a Diplosomid may 

 have two or many spermatic vesicles provided its vas deferens 

 be straight. 



A via media between the two latter alternatives seems best ; 

 and in this I am further encouraged by the fact that Jourdain 

 has proposed to unite the Didemnidae and Diplosomidae under 

 the title Oligosomidae (see " Challenger " Eep., pt. xxxviii., 

 page 307). I propose to keep the Ccelocormidae distinct, on 

 account of the highly-specialised ascidiarium, and to unite the 

 genera now ranged under the DidemnidEe and Diplosomidae 

 with Polysyncraton under the single family proposed by 

 Jourdain but disallowed by Herdman. The genera Didem- 

 num and Leptoclinum might then form one genus, and the 

 Diplosomoides and Diplosoma another. The genus Enccelium 

 may perhaps remain distinct. 



The characters of the family Oligosomidae would then run 

 as follows : — 



Corm thin, flat, incrusting, never pedunculated. 



Systems irregular or absent. Common cloacal apertures 

 usually conspicuous. 



Zooids small, and very distinctly separated into thorax and 

 abdomen. 



Test gelatinous or cartilaginous, usually containing stellate 

 calcareous spicules. Ectodermal prolongations well developed 

 and muscular. 



Branchial siphon variable, frequently six-lobed. 



Stigmata usually in four, sometimes three rows. 



Atrial pore plain or with a languet. 



Eeproductive organs variable. Male consisting of one or 

 more spermatic vesicles, with a vas deferens usually spirally 

 coiled. 



Gemmation pyloric. 



The genus Dlplosoma would then probably indicate the 



