2o8 Papers from the Marine Biological Laboratory at Tortugas. 



movement of the spermatozoon is comparatively slow and is not long 

 continued, for it soon attaches itself, by means of its tail-piece, to the glass 

 slide or other object on which it is being observed. As soon as this occurs, 

 the contraction waves pass down both the membranes simultaneously and 

 they then become much shorter and faster. With the spermatozoon 

 attached in this way, the membranes may continue to be active for a time 

 which varies with the medium used. In sea-water, contractions of the 

 membranes were still seen after two hours, in isotonic NaCl after five hours, 

 but in isotonic MgCU they were very quickly inhibited. It very frequently 

 happens, however, that the tail-piece breaks off and the spermatozoon 

 swims away with a very much more rapid movement than it had at first. 



When the tail-piece begins to break it can be seen to be composed of a 

 number of fused flagella; sometimes, as the spermatozoon moves away a 

 few of these flagella still adhere to it. This probably explains the statement 

 of Brock to the effect that a tuft of flagella, which is invisibile at first, is to be 

 seen after the spermatozoon has been swimming about for a while. 



The first indication of breakdown in the spermatozoon occurs among 

 the albuminous bodies, in that they gradually disappear. The process is 

 undoubtedly one of liquefaction, for they leave in their stead a brownish 

 semi-fluid substance in which, however, may still be seen the outlines of 

 these bodies. When this has occurred one can observe for the first time the 

 myoneme-like striations that are present on the cell-wall. Accompanying 

 the disappearance of the albuminous bodies, there is a general flattening 

 of the cell-body and the membranes. Undulations of the membranes con- 

 tinue a long time after this flattening has taken place and lead eventually 

 to a partial separation of the membranes from the cell-wall. After this 

 their disintegration is rapid. 



The shape of the apyrene spermatozoa of Strombus bituberculatus is 

 very constant and the variations in size that occur are very slight. From 

 the centrosomal plate to the tip of the tail-piece the spermatozoa measure 

 about 90 micra; the width of the membrane is usually about 5 micra and 

 the greatest diameter of the cell-body averages about 8 micra. In S. 

 costatus the apyrene spermatozoa are much longer, measuring 120 to 125 

 micra, but the other dimensions are not increased proportionately; according 

 to Brock's statement they attain a length of 180 micra in 5. lentiginosus. 

 The apyrene spermatozoa in S. bituberculatus and in S. costatus are greatly 

 outnumbered by the eupyrene. Brock has estimated the numerical relation 

 between them to be about i to 500 for S. lentiginosus. 



Because of the failure to obtain ripe eggs of Strombus at the time of the 

 year when the material for this investigation was collected (March to the 

 middle of May), it was impossible to determine experimentally whether or 

 not the apyrene spermatozoa have any function with regard to the eggs. 

 Ripe eggs of several sea-urchins were to be had in great abundance, how- 

 ever, and those of Tripneustes were mixed with some of the contents of the 

 sperm-duct of Strombus. The presence of the eggs had no effect whatever 



