512 W. H. Coe — Anatomy of Cerehratulus lacteus. 



Figure 10. — Cross section of the main longitudinal nephridial canal (m) and its close 

 relation with the lateral lacuna {II) in Cerehratulus Leyclii ; x 225. 



Figure 11. — Blood-corpuscles; x 500. 



Figure 12. — Cross section of a small nephridial canal. The section is rather thick and 

 the nuclei of the ceUs do not appear as regular as is often the case. Ciha or cell-walls 

 are not seen ; x 225. 



Figure 13. — Cross section of a contractile blood-vessel with its regular coating of 

 parenchyma- eel Is (pc). The muscles (m) outside the endothelium (ew') are con- 

 nected with radial fibres of connective tissue (7/) which hold the vessel in place ; 

 X 225. 



Figure 14. — Longitudinal section of a blood-vessel. The parenchyma-cells do not 

 appear so sharply marked off as in a cross sectiou ; x 225. 



Plate XIV. 



Figure 1. — Horizontal section of the side-organ showing the ciliated canal (cc) cut trans- 

 versely in its ascending portion ; ccf posterior portion of ^ame canal cut obliquely. 

 The fibrous core (fc^) is directly continuous with that of the dorsal brain-lobe. 

 Large areas of ganglion-cells (gc), like those of the first type in the brain, are seen 

 on the right and left sides. A thick mass of large gland-cells (g) occupies the 

 anterior and posterior borders ; c, sheath of connective tissue covering the whole; 

 X 150. 



Figure 2. — Section of the ciliated canal, more highly magnified ; n, nuclei of the greatly 

 elongated "median" cells {mc\ far removed from the lumen of the canal {cc). 

 Around the lumen of the canal are two dark lines, the inner being caused by the 

 thickening of the cilia at this point, and the outer being made up of the borders of 

 the cells; k% inner "lateral " cells; k, outer "lateral " cells; /c', fibrous nerve-core 5 

 X 250. 



Figure 3. — One of the "median " cells macerated in formalin ; x 300. 



Figure 4. — Nearly ripe, living ovum after being pressed from the body of the animal ; 

 y, zona pellucida. The transparent germinal vesicle contains a large germinal 

 spot ; X 50. 



Figure 5. — Portion of an ovary with developing ova. The large ova {ov^) lie against 

 the connective tissue framework (c) and are surrounded by a follicle (/<?) of flattened 

 epithelial cells ; x 50, 



Figure 6. — Portion of a spermary with developing spermatozoa . The layers of cells are 

 commonly much thicker than is here represented (only the nuclei of the cells are 

 shown) ; sc, several layers of large " mother-cells " internal to the cormective tissue 

 framework; sc', smaller cells derived from the division of the "mother-cells"; sc" 

 smaller, somewhat elongated cells which probably develop directly into spermato- 

 zoa which fill the lumen of the spermary; x 500. 



Figure 7. — Ripe spermatozoa; x 800. 



Figure 8. — Sagittal section through a portion of the intestinal region of the body; ic, 

 intestinal cseca, separated by thick bands of dorso-ventral muscles {dm); av 

 anastomosing blood-vessels seen above and below each intestinal csecum (these are 

 paired vessels uniting the dorsal with the lateral vessels : see Plate XIII, fig. I) ; 

 gd, gelatinous tissue; Im, inner layer of longitudinal muscles of body-wall. From 

 a small specimen ; x 40. 



