44 ÏHOS. H. MONTGOMERY, 



Plate 2. 



Fig. 16. Cerébratulus. Half of a cross section through the pos- 

 terior quarter of the caudicle, showing the abundance of the mesenchym 

 tissue {Mes). Del. haematoxylin, eosin. (Obj. C, oc. 2.) 



Fig. 17. Cerébratulus. Free mesenchym cells of the body cavity. 

 Ehelich-Biondi stain. (Homogen, immers., oc. 4.) 



Fig. 18. Cerébratulus. Cross section of the lateral nerve chord 

 (N.C) in the posterior quarter of the caudicle, showing its envelope of 

 mesenchym cells (Mes) ; cf. Fig. 1 6. Del. haematoxylin , eosin. 

 (Homogen, immers., oc. 2.) In these cells, the chromatin of nearly every 

 nucleus is directed towards the nerve chord. 



Fig. 19. Cerébratulus. Dorsal, lateral, and ventral segments of 

 one cross section through the body wall. Ehrlich's Haematoxylin, 

 eosin. (Obj. A, oc. 2.) All show the body cavity (B.C). 19 a. Seg- 

 ment enclosing the proboscis sheath {P.S) and dorsal blood vessel 

 (D.V). 19b. Lateral segment enclosing the lateral nerve chord (N.C), 

 and portions of the commissures (V.C) of the bloodvessels. 19 c. Ven- 

 tral segment enclosing the two lateral blood vessels (L. V). 



Fig. 20. Cerébratulus. Network of mesenchym cells in the body 

 cavity. Ehrlich-Biondi stain. (Homogen, immers., oc. 2.) 



Fig. 21. Cerébratulus. Cross section of parenchym cells (Par), 

 between the proboscis sheath (P.S) and the dorsal blood vessel (D. Y), 

 cf. Fig. 19 a. Ehelich-Biondi stain. (Homogen, immers., oc. 2.) 



Fig. 22. Cerébratulus. Portion of a cross section through the 

 outer layer of inner longitudinal musculature, showing the pseudo- 

 epithelium of mesenchym cells applied against it. Certain of the cells, 

 and their nuclei (N) are greatly increased in size, through the ac- 

 cumulation of nutritive particles (Nutr), cf. Figs. 17, 20. Ehrlich- 

 Biondi stain. (Homogen, immers., oc. 4.) 



Plate 3. 



Fig. 23. Lineus gesserensis. Parenchym cells (Par) in the cir- 

 cular musculature of the proboscis sheath, and on the dorsal periphery 

 of the dorsal blood vessel (D.V). Ehrlich-Biondi stain. (Homogen, 

 immers., oc. 2.) 



Fig. 24. Lineus gesser. Pigmented connective tissue cells of 

 the body muscular wall. Del. haematoxylin, eosin. (Homogen, im- 

 mers., oc. 4.) 



Fig. 25. Lineus gesser. Half of a cross section through the 

 posterior quarter of the body, from an immature individual with ex- 

 ceptionately large body cavity (B.C). (Obj. A, oc. 4.) Del. haema- 

 toxylin, cochineal. 



Fig. 26. Lineus gesser. Network of mesenchym cells from the 

 body cavity. Del. haematoxylin, cochineal. (Homogen, immers., oc. 4.) 



Fig. 27. Lineus gesser. Intracapsular connective tissue cell, with 

 nuclei of other cells, from the fibrous core of the lateral nerve chord. 

 Del. haematoxylin, eosin. (Homogen, immers., oc. 4. 



