E. W. BERGER ON THE CUBOMEDUS^E. 69 



presence or absence of this secretion is evidently correlated with the 

 feeding habits of the animals, or else it would be more generally 

 present. 



The endothelium is thickest (the cells are longest) in the upper 

 part of the ampulla where the supporting lamella approaches the 

 lens of the proximal complex eye, and in the lower portion of the 

 ampulla (Fig. 7), in the angle between the concretion cavity and 

 the region of the distal complex eye. In general, the cells are 

 longest in the upper part of the ampulla, while in the lower part, 

 especially where they cover the concretion cavity and the dorsal 

 wall, they may be quite cubical instead of columnar. Often they 

 present a vacuolated appearance at their bases (Fig. 27). Glaus and 

 Schewiakoff describe and figure this endothelium, but not in detail. 

 No one, to my knowledge, has described this secretory function. 



The nuclei of these cells are peculiar. They may contain a 

 network with a nucleus (Fig. 27). Again, they may show evidence 

 of amitotic division (Fig. 20, h, i, j). Indeed, Remak's scheme (Wil- 

 son 18 "The Cell," p. 4(3) can be quite readily demonstrated. It is, 

 however, such dumbbell-shaped, elliptical, or ringed nuclei as seen 

 in Figs. 7 and 20 that are of special interest. 



I have spoken of some of these nuclei as dumbbell-shaped, 

 elliptical, or ringed. This is so, however, only in sections. They are 

 really flattened spheres with a rod of tissue, of the same structure 

 as the nuclear wall, stretching between the poles. One may con- 

 veniently compare the shape of these nuclei with that of an apple, 

 the core of the apple representing the rod connecting the two opposite 

 flattened or slightly hollowed poles of the nucleus. For convenience 

 I shall call the rod connecting the two poles the axis of the 

 nucleus. The dumbbell or elliptical shape would be obtained by a 

 meridional section through the axis (Figs. 20, a, b, c, e, g, k, 1, m, n, 

 o, 7). Likewise a ringed appearance with a central dot would be 

 obtained by a section parallel with the flattened surfaces or perpen- 

 dicular to the axis (Figs. 20, d, 7). In a section not strictly meridional 

 the axis would be cut as in Fig. 29, a, or not show at all. As nearly 

 as I could determine, the inside of these nuclei is a vacuole, which 

 the axis penetrates. 



The walls and axis of these nuclei have the structure of a very 

 fine and dense network that stains very dark with iron-haematoxylin. 

 It stains quite like the reticulum of any nucleus, but is very dense, 



