Papers from the Marine Biological Laboratory at Tortiigas. 225 



grown across the cell. In later stages they are formed in increasing numbers 

 and gradually come to fill up first the middle and then finally the posterior 

 portion of the spermatosome (figs. 48, 49, 63, and 64; also figa. 1-6). By 

 the time that all the chromatin has disappeared from the cell, practically 

 all of the albuminous bodies have been formed (fig. 64). 



The formation of the albuminous bodies takes place in very much the 

 same way as Kuschakewitsch ('11) has described for the apyrene sperma- 

 tozoon of Vermetus and which has been briefly reviewed on page 204. 

 In Strombus there is not a general differentiation of the cytoplasm into a 

 large number of thick-walled chambers. Instead, there is a continual for- 

 mation of occasional vacuoles throughout the cell, those that are first formed 

 filling up rapidly with the secreted albumen before the later ones have 

 appeared. For this reason one never sees more than three or four vacuo! 2S 

 in any one given cell (figs. 43, 47, and 49). The extreme vacuolization 

 shown in figure 46 is due to imperfect fixation and is not a natural condition. 

 The process of the secretion of the albuminous bodies can be followed most 

 readily in the posterior region of the spermatosome. 



In a vacuole such as one of those shown in figure 49, a matrix is laid 

 down composed of a substance which has a marked affinity for nuclear 

 stains. The appearance of this matrix differs to some extent with the 

 degree of "osmication " which the cell has undergone. In the inner portions 

 of the tissue it is seen to be composed of a number of very irregular, darkly 

 staining masses (fig. 52), while in the outer portion it appears to have the 

 form of a network (fig. 63). It must be borne in mind that the magni- 

 fication in figures 63-65 is less than in the preceding figures. Between 

 these two extremes there stands a condition in which the network is made 

 up of granules. Around this substance a clearer, homogeneous material is 

 secreted, which gradually fills up the vacuole and effaces the matrix. In 

 many instances narrow strands can be seen connecting this substance 

 (an albumen?) with the surrounding cytoplasm (figs. 46, 49, and 54). 



When the vacuole has been completely filled, a membrane is formed 

 around the secretion, the body assuming a spherical shape. The bodies 

 now give up their stain (iron haemotoxylin) very readily; in the places where 

 the spermatosome has been strongly "osmicated," they either appear 

 unstained and yellow, or else they show the characteristic "Spiegelfarbung" 

 of yolk granules. As has been stated, their change to the hexagonal shape 

 seen in the adult condition is due to the pressure they exert upon one 

 another after they have completely filled the spermatosome and the latter 

 has undergone its final elongation and constriction. 



By far the most striking changes that begin to take place at the time 

 when the distal centrioles reach the cell membrane (figs. 44 and 45) are 

 those which result from the continued growth of the axial fibers, viz., the 

 formation of the undulating membrane and the resulting changes in the 

 size and shape of the spermatosome. Having come to extend entirely 

 across the cell, the bundle of axial fibers, by their continued growth, begins 



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