176 On the Tentacles of Nautilus pompilius. 



conditions, possibly connected with reproductive processes. 

 The sensory function is probably the same in both sexes and 

 continually active, though it is possible that this also may be 

 closely connected with reproduction. 



The structure of the hectocotylus (or spadix) has recently 

 been admirably described by Vayssiere. Still, there are 

 several points which may be added to his description. 



The hectocotylus is composed of a group of four tentacles. 

 These become highly modified. The organ is usually situated 

 upon the left side ; but in between twenty and twenty-five 

 per cent, of my specimens it is upon the right side. In one 

 case hectocotyli are upon both sides. On the opposite side 

 of the animal from the hectocotylus is a similar group of 

 lour tentacles, but unmodified. 



Three of the tentacles forming the hectocotylus are closely 

 enveloped by a fleshy sheath, the fourth and smallest only 

 partly. On the external side of the sheath at the margin is a 

 circular glandular area. The glands are compound-tubular, 

 branched quite simply; they extend, in a direction perpen- 

 dicular to the surface, about three quarters of the distance 

 through the sheath. Upon examining the corresponding 

 portion of the sheath of the similar group of the opposite side 

 I found a glandular area in the same position as that upon 

 the sheath of the hectocotylus. The area is smaller, the 

 glands are less developed, yet are exactly similar in structure. 

 The presence of this gland on both groups of tentacles is 

 extremely interesting, as it may indicate an original hecto- 

 cotylization of both groups. 



In the second tentacle of the hectocotylus (the tenth cirrus 

 of Vayssiere) is another interesting series of glands. This 

 tentacle is annulated, the grooves being deepest upon the 

 upperside. Into each groove upon this side opens a row of 

 perfectly simple sac-like glands. The openings are ex- 

 ceedingly small and are well hidden in the depths of the 

 grooves. A single layer of columnar epithelial cells lines the 

 gland. The cells of the neck of the gland are low, but they 

 rapidly increase in height as they pass into the gland, so that 

 the body of the gland is lined by exceedingly high cylin- 

 drical cells. 



[The valuable material upon which these notes are based 

 was presented to the Department of Animal Biology of the 

 University of Minnesota by Mr. Louis Menage, and I am 

 greatly indebted to Professor Nachtrieb for placing it at my 



