220 INTRODUCTION TO CYTOLOGY 



then continues along the nuclear membrane on the other side, following 

 the path of the centrioles, and eventually comes to lie near them. 



During the migration of the acroblast an acrosome is differentiated 

 from it. This first appears as a delicate vesicle on the side of the acro- 

 blast near to the nucleus and seems to consist of a new material, the 

 formation of which is dependent upon the activity of the substance of the 

 acroblast.-^ Within it is a small granule. Very rarely the acrosome 

 itself has the form of a granule rather than a vesicle (mollusks, Gatenby ; 

 grasshopper. Bo wen). The acroblast becomes somewhat smaller as the 

 acrosome grows, and together they move again toward the anterior end 

 of the cell. Either before or after reaching the apex they separate, the 

 acrosome taking its final position near the apex while the remainder of 

 the acroblast, known as the "Golgi remnant," passes backward along the 

 tail and is ultimately cast out of the cell in a protoplasmic ball sloughed 

 off at the close of spermiogenesis.^^ 



The acrosome, after reaching its definitive position near the anterior 

 end, undergoes a further differentiation. Within it appears a deeply 

 staining mass which may possibly bear some relation to the granule 

 observed in the vesicular acrosome at earlier stages. It rapidly develops 

 into the pointed perforatorium at the tip of the spermatozoon, while the 

 remaining portion of the acrosome grows backward as a band against one 

 side of the asymmetrical and elongating nucleus, with which it becomes 

 very intimately united as the spermatozoon matures. It is the view of 

 Bo wen (19246) that the acrosome or perforatorium is not merely a boring 

 organ, as commonly thought, but a secretion with a special function in 

 fertilization, thus corresponding in origin with the secretion droplets 

 observed to arise in connection with the Golgi material in gland cells 

 (p. 76). Van Herwerden has shown the presence of an oxidase in the 

 acrosome region. Certainly the acrosome cannot be a boring organ in the 

 spermatozoon of Lepisma, in which it lies at the base of the nucleus rather 

 than anterior to it. 



Nucleus. — No conspicuous changes occur within the nucleus until the 

 acroblast and its differentiated acrosome have completed part or all of 



23 In Lepidoptera and grasshoppers the Golgi bodies do not fuse but give rise to a 

 common acrosome (Bowen, 1922ae). Parat (1928) regards the acrosome as a vacuole, 

 largely because it stains with neutral red. Pollister (1930) finds no neutral-red stain- 

 ing substance in Gerris from the close of the first spermatocyte division to the formation 

 of the acroblast in the spermatid; it then appears as a secretion within the acroblast. 

 H. Johnson (1932) finds the chondriosomes and the chromophilic rim of the dictyo- 

 somes in insect spermatocytes to react similarly to Janus green and certain other vital 

 dyes and questions the complete homology of the dictyosome-acroblast complex with 

 the somatic Golgi apparatus. 



2" Sjovall (1906) on the guinea pig, Terni (1914) on Geotriton, Gatenby (1917) on 

 mollusks and Lepidoptera. In certain mammals a portion of the Golgi remnant is 

 said to remain as a part of the middle piece (Weigl, 1912; Gatenby and Woodger, 

 1921). 



