MITOCHONDRIA ASCARIS. 257 



Fate of the 'refringent vesicles.' 



During the first maturation division, the 'vesicles' arrange them- 

 selves in radiating rows parallel to the astral rays and each assumes 

 an oval form (Figs. 3 and 4). In the center of each of these granules, 

 after careful destaining, can be seen short, deeply staining, granular 

 rod-like bodies (Fig. 5) that run lengthwise of the vesicle. The begin- 

 ning of the second maturation division finds the elongation of the 

 refringent vesicles very pronounced, the vesicles being from three to 

 four times as long as broad. As the second division goes on, the 

 vesicles take a very marked peripheral position with their long axes 

 perpendicular to the cell membrane (Figs. 6 and 7), leaving a clear 

 perinuclear space filled with small granules. These are the 'micro- 

 somes' of Van Beneden and the 'plastochondria' of later writers. 

 At the same time the rod-like granular bodies within the refringent 

 vesicles disappear. Both INIeves and Romeis have clearly shown that 

 these bodies and the 'plastochondria' are identical structures in the 

 case of A. megalocephala. They certainly have the same staining 

 reactions in Benda's and Elu-lich-Biondi stains, and there can be little 

 doubt but that they are also identical with the bodies seen in A. mega- 

 locephala. 



The process of 'cytoplasmic reduction' takes place shortly after 

 the second division has been completed, but no refringent vesicles are 

 lost with the extruded cytoplasm, only a considerable number of the 

 small granules derived from the vesicles at the time of the second 

 division. The spermatid is thus reduced by at least one third of its 

 original volume, the refringent vesicles becoming very closely packed 

 together. The vesicles now fuse into irregularly shaped bodies that 

 soon round up into highly refractive spheres (Figs. 8 and 9). These 

 larger spheres again fuse with one another, forming a hollow sphere 

 of globules surromiding the nucleus (Fig. 10). The globules, in under- 

 going further fusion, move towards one end of the spermatid, leaving 

 the nucleus and its surrounding plastochondria lying free in the cyto- 

 plasm (Fig. 11). In Benda's stain these globules now begin to lose the 

 blue color and to take on the yellow stain of yolk material, showing that 

 the karyochondrial material is gradually being changed into food. 

 Fusion continues until a single hemispherical body, slightly concave 

 on the side next to the nucleus, is formed (Fig. 12). This body is the 

 'refractive body' and is fully formed in the mature spermatozoon 

 just before copulation takes place. Its chemical make-up is almost 

 entirely that of yolk material. 



