302 Mr. H. M. Bernard on 



ago, shows the sperm-forming centres. The original speci- 

 men is just under 3 centim. long, and is peculiar in one point, 

 Avhich from the first attracted my attention : the alimentary 

 canal is distended with fine grit. In this very little can be 

 found which looks like organic matter from which nourish- 

 ment could be obtained. The animal had apparently sought 

 to allay the pangs of hunger by swallowing enormous quan- 

 tities of fine mud *. This mud shows as a broad black or 

 brown streak along the section, and the particles of it have 

 unfortunately escaped in the process of cutting and mounting 

 and have spoiled many of the slides. The alimentary canal, 

 thus heavily weighted with inorganic matter, has changed 

 its position. It runs along close under the dorsal surface, 

 having displaced all tlie branching tubules of the genital 

 gland which normally arch over it dorsally. The whole 

 genital gland now lies below the intestinal canal and probably 

 partially at its sides. This dorsal position of the weighted 

 alimentary canal is doubtless due to the habit of the animal 

 of swimming always on its back. 



Fig. 6 (PI. XII.) shows portions of four branches of the 

 genital tube and a ripe egg (e) cut through. One branch con- 

 tains a ripe egg in its passage along the tube (only partially 

 shown), while two of them {dt) show portions of the epithelium 

 dissolved into sperm-cells. One of these is cut transversely 

 and the other longitudinally. The part drawn is in the 

 region of the eighteenth to nineteenth appendage, i. e. not 

 far from the genital duct. Fig. 7 is a magnification of part 

 of the longitudinally-cut branch shown in fig. 6, as seen 

 under the oil immersion objective. The transition between 

 the normal epithelial cells and the masses of sperm-cells is 

 quite sudden, and the reduction of the cells has given rise 

 to the usual slime-globules. The sperm-cells again measure 

 from 4 to 5 /i. 



Fig. 8 shows a portion of the main or axial tube of the 

 genital gland some way behind the duct leading to the exte- 

 rior. A small pocket is seen on the ventral side, bulging 

 down the basal membrane. In the next section in one direc- 

 tion this pocket is nearly flattened out. I did not come 

 across it again in any other section. In the centre of the tube 

 is a large egg (e) squeezed out lengthways and perhaps cut 

 tangentially ; the slimy covering of the egg, hardened by the 

 alcohol, has been broken up by the microtome-razor. In 

 this case the egg is certainly ripe, and, if the sperm-cells are 



* It is worth remarking that tlie Trilobites Lad, under certain circum- 

 stances, the same habit. Strands of argillaceous matter have been found 

 running through the fossils (Barrande). 



