Genera of Uncertain Position. 



121 



similarly constituted as shown in figs. 12 and 13. This entire absence of muscles constitutes 

 an important difference to the other Khizocephala. 



We must next remark the great poverty of lacunar and connective tissue in the vis- 

 ceral mass, comparatively to other Khizocephala. That part of the visceral mass which is not 

 occupied by the ovaries contains merely a coagulated fluid (fig. 12 vise). The only position 

 in which lacunar tissue is well developed is in the mesentery immediately surrounding the 



•m. 

 Text fig. 24. 



mesenteric canal (figs. 12, 15, 16 and 17 lac). I take this peculiar restriction of lacunar 

 tissue to be connected with the absence of a root system and the method of nourishment by 

 the mesenteric canal. 



The structure of the mesenteric canal is indicated in figs. 12, 15, 10, 17 mes.can. 

 It is lined internally by a layer of chitin continuous through the whole canal, passing poste- 

 riorly at the stalk into the external chitinous investment of the body and anteriorly into the 

 internal chitinous investment of the mantle cavity. Externally to the chitin is an ectodermal 

 epithelium of columnar cells, shown in longitudinal section in fig. ! 5, and in transverse section 

 in fig. 1(3. Surrounding this epithelium is the lacunar tissue (lac). The posterior opening of 

 the mesenteric canal at the end of the stalk is shown in transverse section in fig. 17. 



The minute structure of the ovaries which are two in number is exactly similar to 

 that in other Rhizocephala (fig. 13 ov.); we have an ovarian epithelium externally and within 

 a large number of eggs in various stages of development. 



The colleteric glands have the histological character shown in fig. 13 coll; the cells 

 are highly columnar and the nuclei have their chromatin dispersed in granules. They do 

 not differ greatly from the simple colleteric glands of such a genus as Peltoyaster, save in 

 their position as external discs on the surface of the visceral mass. 



Zoul. Station zu Neapel. Fauna und Flora, Golf von Neapel. Rhizocej'lialj. l(i 



