12 THOS. H. MONTGOMERY, 



mesenchym cells, and the unstaining spaces between them, the struc- 

 tureless fluid, with which the cavity is probably filled in life. A 

 pseudoepithelial lining of the body cavity formed by mesenchym cells, 

 as we find in Cerebratulus, is absent in Carinella ; for in this species 

 in fact, even in the posterior body region, the blood vessels, intestine, 

 and the inner surface of the longitudinal muscle layer, are covered by 

 a layer of the last described connective tissue. 



Around each gonad (a S examined) is a fibrous membrane con- 

 taining deeply staining nuclei, some with, some without the refractive 

 granular mass mentioned above ; I have been unable to decide whether 

 the cells of this membrane are products of mesenchym cells, or of 

 the previously described connective tissue cells. As I had no im- 

 mature individuals for study, I can offer no new facts as to the 

 derivation of the genital cells themselves; Bürger ('90) states that 

 the genital cells develop simultaneously with the gonadal membrane. 

 But early stages of genital cells being found in proximity of the 

 mesenchym cells (Figs. 3, 7), they are probably derived from the 

 latter. 



The mesenchym tissue and the connective tissue with intercellular 

 substance, are structurally very similar, their main difference being 

 the absence of intercellular substance in the former. As we have 

 seen, in both the nucleus lies usually in or upon a refractive, granular 

 mass (cf. Figs. 3, 7 with Figs. 6 a — d). I have found these granules 

 also within the nucleus, causing an enlargement of the latter — as 

 in the case with the granules in the mesenchym cells of Cerebratulus ; 

 therefore it is probable that they are concerned in the nutritive pro- 

 cess of the cell. These granular masses are characteristic of these 

 two tissues, being found elsewhere only in the blood and rhyncho- 

 coelomic corpuscles, but there with a different color reaction to the 

 Ehrlich-Biondi stain. 



3) The parenchym tissue in the anterior region of the 

 body, forms a layer around the ventral and lateral surfaces of the 

 proboscis sheath (absent on its dorsal aspect), an interrupted layer 

 on the dorsal part of the intestine, an interrupted layer around the 

 rhynchocoelomic blood vessels, and a mass of cells around the lateral 

 blood vessels (except upon their outer side) ; also groups of paren- 

 chym cells lie in the inner circular muscle layer, between the intestine 

 and proboscis sheath. Only those cells surrounding the lateral vessels 

 come into contact with the longitudinal muscle layer of the body 

 wall, the rest of this tissue lying mainly within (internally from) the 



