300 Mr. H. M. Bernard on 



indications of these sperm-cells having originated from a cell 

 or cells close to the basement membrane, which were arched 

 over by the adjoining epithelial cells. Further, Moore (loc. 

 cit. supra) has pointed out that in the egg-formation the eggs 

 develop very irregularly out of ordinary epithelial cells. It 

 is obvious that we have the same indifference in the formation 

 of the sperm-cells, for in the completely disorganized portion 

 of the tube every single epithelial cell, whether arched over or 

 not, must have divided into exactly similar sperm-cells. It 

 looks as if the distal ends of the cells break down into 

 slime, and the proximal ends divide up into sperm-cells. This, 

 it seems to me, would necessarily involve the arching over 

 of those which start the process first. 



Lepidurus productus. 



I have only one complete series of longitudinal sections of 

 Lepidurus productus. The section is 23 millim. long ; but 

 as the animal was slightly bent, it probably measured 

 25 to 26 millim. 



Fig. 5 is one of four or five pocket-like outgrowths found 

 in a section passing well through the genital gland. This 

 one was selected because it happened to be cut through longi- 

 tudinally. It is situated quite anteriorly in the body and 

 dorsally. The rest are scattered about without any apparent 

 order on the section. There is no marked localization of the 

 sperm-forming area at the posterior tip of the gland, as in 

 L. glacialis and its minute Spitzbergen variety. Indeed, in 

 this animal and in Apus cancriformis the branching of the 

 tube is so pronounced that it is not easy to ascertain which is 

 the posterior tip of the gland. Two pockets, however, were 

 found opening into the axial canal in the region of the 

 eighteenth appendage, i. e. very near the duct which dis- 

 charges the eggs into the egg-pouch. 



The figure speaks for itself; there is no special arching of 

 epithelial cells over the aperture, but in the same section 

 three low cells or groups of cells (e) close down on the base- 

 ment membrane are seen arched over by the adjoining cells 

 and apparently about to develop into eggs or perhaps into 

 masses of sperm-cells. 



Figure 5 a is a very small pocket, which looks as if it 

 might have been produced by the division of one, or at the 

 most of two, cells over which the adjoining epithelial cells 

 had arched. The proliferation of the sperm-cells, instead of 

 forcing up the arched epithelial cells, bulges out the basement 

 membrane. This figure is given because it again shows that 



