134 REPORTS ON INVESTIGATIONS AND PROJECTS. 



rene spermatozoa are present, there is a cell very similar to the oligopyrene 

 spermatocyte of Paliidina. This develops into a nurse-cell to which sperma- 

 tozoa become attached and which, together with the latter, moves into the 

 sperm-duct. It was with the purpose of studying these cells in a live condi- 

 tion, and also of collecting whatever material I could for the study of oligo- 

 pyrene spermatogenesis, that I went to Port Royal, Jamaica. 



Kingston Harbor abounds with many prosobranchs, among which are at 

 least three species of Littorina. After a thorough examination I found that 

 those snails which live above water-mark for any length of time do not have 

 oligopyrene spermatozoa, and I think it may be held in general to be true 

 that the dimorphism of the male sex-cells among prosobranchs occurs only 

 in some of those which live below the surface of the water. Urosalpinx 

 may constitute an exception, but if it is not covered with water it is under a 

 moist stone or other object and not exposed to view. Among the snails which 

 have oligopyrene spermatozoa and are easily obtainable in the vicinity of 

 Kingston Harbor are Murex sp., Pteroceras sp., and several species of Strom- 

 bus. My work, however, was confined to Littorina and Strombus. 



The contents of the sperm-duct of Littorina nebulosa, when diluted with 

 sea-water, appear under the microscope as a great number of spheres, to each 

 of which is attached a tuft of spermatozoa. These spheres are composed of 

 a number of large granules inclosed in a membrane, and among them is a 

 very degenerate nucleus ; this may be demonstrated by straining intra vitam 

 with methylene blue. On one side there is an agglutinous pabulum into which 

 are inserted the heads of the spermatozoa. The first movement to be seen 

 is a rhythmical and uniform beating of the entire tuft; this sends the nurse- 

 cell forward. Presently the tuft spreads and then each spermatozoon beats 

 independently of the others. In case two or more tufts meet, the spermato- 

 zoa become entangled with each other and the nurse -cells are drawn together 

 and held by the sticky substance into which the former are inserted. From 

 a mass such as this the tails of the spermatozoa will be seen protruding on 

 all sides and beating like cilia. They will remain alive in this condition for 

 several hours. 



Up to a very late stage in their development these cells retain a connection, 

 by means of a long stalk, with the wall of the testis. Small granules of yolk 

 matter pass up the stalk and are dissolved in the cytoplasm of the cell. The 

 nucleus soon begins to degenerate and various areas of the cytoplasm are 

 seen to diflferentiate into large granules. These finally fill up the body of 

 the cell, and the nucleus, which by this time has the appearance of an empty, 

 crumpled shell, is pushed to one side. Probably as the stalk snaps it draws 

 up a large number of spermatozoa after it towards the cell-body. Although 

 at present I can not make the assertion that these cells originate in the same 

 way as I have described for the oligopyrene spermatocytes of Paludina, the 

 evidence I have seen seems to indicate that to be the case. As to their func- 

 tion, they undoubtedly serve as nurse-cells to the spermatozoa while the lat- 

 ter are in the sperm-duct. Sections of the winter testis of Littorina rudis 

 show the sperm-duct full of spermatozoa and of nurse-cells which are in a 

 more or less exhausted condition. 



While at Port Royal, with ample material at hand, I had an excellent 

 opportunity of making a thorough study of the oligopyrene spermatozoon of 

 Strombus in a live condition. Brock has described and figured it, but not 

 quite accurately. The spermatozoon in this case is larger and of a more 

 complex structure than that of either Paludina or Urosalpinx. The head is 



