76 



CERIANTHARIA. 



found aggregated at the aboral end of the ciliated tract region, forming bunches. These bundles 

 answer to the wavy coils of the cnido-glandular tract. 



2) Craspedonemes which possess only an ascending limb of the filament (Textfig. 13). This 

 is the case in P. iiiaua. Here evidently the filament ha.s not yet reached the aboral side of the cras- 

 pedoneme in the course of its growth. 



The cnido-glandular tract more rarely forms a craspedoneme and only on mesenteries 

 whose cnido-glandular tract region is extremely slight. This is so with certain mesenteries of Pacliy- 

 ccrianthus solitariiis (Textfig. 14) and sometimes in Ccriaiitlius lloydii. vStill the wavy coils of the 

 cnido-glandular tract correspond, as already mentioned, to the bunches in the ciliated tract, though 

 they may not display such thread-like formations as the ciliated tract, but even so the cnido-glan- 

 dular tract traverses processes of mesenterial entoderm and nresogloea. 



The craspedonemes of the craspedion region are met with partly in the form of acontia 

 partly in the form of craspedonemes undifferentiated in outward appearance. 



The "acontia" are rounded in transverse section. The filamentous part consists mainly of 

 mucus cells: they are provided with an ectodermal muscle layer. In the endoderm numerous nema- 

 tocysts ma}- sometimes (often?) be developed. Typical "acontia" arc found in ^Irachnantliits and in 

 AracIiiKictis albida (Textfigure 15). 



The more undifferentiated crasi^edon emes of the craspedion region retain ]>artially the 

 nnicus cells and spirocysts, but have developed in addition granular gland cells and thick-walled 

 neniatocvsts. Such craspedonemes have hitherto been met with only in Ccriaiitlicopsis aiiuricanns 

 (Textfigure 16). 



Finally, as modified craspedonemes of the craspedion region may be regarded the Botru- 

 cnidae. Typical botrucnidae are found in Botriioiidifcr norvcgiciis and in many of van Beneden's 

 Ceriantharia-larval forms (Textfigure 11). 



■■^•KS"®*®^'*- 



