Tentacles of Nautilus pompilius. 175 



tubular type. The epithelial cells of both glands and lamella* 

 are tall and cylindrical. The cells of the lamellae are for the 

 most part heavily loaded with secretory products. The cells 

 of the glands are also loaded. Yet the lumens of the glands, 

 as well as the central cavity, are entirely free from secretion, 

 this evidently being stored in the cells till needed for some 

 unusual purpose. 



Another kind of cell is found among the epithelial cells of 

 both glands and lamellae. Around each epithelial cell are 

 several fine hair-like sensory cells. The middle of each is 

 swollen by the elongated oval nucleus. The tip of each cell 

 is produced into a stiff sensory hair. The immense number 

 of these cells bearing hairs makes the surface appear densely 

 ciliated. The ordinary epithelial cells are of so much greater 

 bulk than the sensory cells that close examination is required 

 to reveal the fact that the cilia do not belong to them. I have 

 seen the bases of the sensory cells continued for some distance 

 into the submucous tissue as fine fibres of about the same 

 diameter as the cell. 



The nerves which innervate Van der Hoeven's organ have 

 the same place of origin as those which innervate the inferior 

 labial lobes of the female. One nerve enters each side of 

 Van der Hoeven's organ and divides into a large number of 

 branches. One of these runs into each lamella and several 

 supply the glandular portion of the organ. 



The number of lamellae of Van der Hoeven's organ closely 

 corresponds to the number of tentacles plus lamellae of the 

 inferior labial lobe. The innervation is the same in each, 

 except that the nerve seems to form all its branches at one 

 point in Van der Hoeven's organ, instead of at two points as 

 in the labial lobe. The musculature of the one is the same 

 as of the other. Willey finds that the same arteries supply 

 both organs, and upon this fact bases the suggestion that they 

 may be homologous. The sensory cells of Van der Hoeven's 

 organ evidently correspond to those found between the bases 

 of the lamellae on the labial lobe ; only in the one case they 

 are restricted to definite areas, while in the other they are 

 scattered throughout the organ. In short, anatomical evidence 

 admits of no conclusion but that Van der Hoeven's organ of 

 the male Nautilus is strictly homologous with the inferior 

 labial lobe of the female Nautilus. 



From the fact that the glandular cells in my sections of 

 Van der Hoeven's organ are nearly all heavily loaded, and 

 that absolutely no secretion is present in the lumens of the 

 glands or in the central cavity of the organ, it appears that 

 its glandular function may be limited to certain times and 



