8 CAPT. C. F. U. MEEK ON THE 



ill scattered groups, and the latter in more closely associated Jbunches. 

 Beyond these are dense masses of ripe spermatozoa, placed at considerable 

 intervals in the lumen of the follicle : the extreme end is occupied by 

 degenerating cells that will undergo no further development. 



The posterior half of the follicle is occupied by unripe and ripe sperma- 

 tozoa, and the greater part of the anterior half is closely packed with the 

 primary spermatocyte growth-stages. The follicle is divided into tracts, in 

 which these various stages are found, the partitions arising from the follicle 

 wall : further subdivision is effected by septa, dividing the tracts into cysts. 

 Cells in one cyst are not all at the same stage ; and the precocious cells of 

 one section correspond with the laggards in the next. When the follicle has 

 been cut at right angles to its length, the succession of stages can be followed 

 with great accuracy until we come to the spermatids, when the identity of 

 the follicle is lost, clusters of spermatozoa alone being distinguishable. 



Spermatogonia. 



The extreme anterior zone of the mature follicles is divisible into two parts, 

 occupied respectively by the primary and secondary spermatogonia. The 

 former are arranged in a single layer round a central cell — the apical cell — 

 recognizable by its regularly ovoid nucleus, in which lies a group of large 

 and deeply staining granules, the ordinary chromatin particles being 

 distributed in irregular blotches. The nuclei of the primary spermatogonia 

 are situate in the region of their cytoplasm furthest from the apical cell, and 

 present a lobulate appearance, as can be seen in fig. 1, on Plate 1. The 

 chromatin is disposed in minute particles upon the linin threads of an 

 apparently complete reticulum ; and I have failed to find any massing of 

 larger granules, as in the case of the apical cell. Each follicle contains one 

 apical cell with its attendant primary spermatogonia. 



At present little is known of the nature of this apical cell, which has been 

 found and studied in many insect forms, but principally in the Lepidoptera ; 

 its function is not yet understood, but it probably plays an important role by 

 affording either nourishment or physical support to the cells destined to 

 become spermatozoa. On the other hand, it has been suggested that it is a 

 degenerate spermatogonial cell, or the mother cell of the primary spermato- 

 gonia surrounding it, or that its function is connected with the formation of 

 the zones into which the follicle portions are subdivided. Davis has found 

 it in the members of the Acrididae and Locustidse that he has studied, and 

 has shown that in Dissosteira Carolina, Arpliia tenebrosa, Cliortophaga 

 viridifasciata, and Stenohothrus curtipenms it is completely surrounded by 

 the single layer of primary spermatogonial cells, but only partly surrounded 

 in Melanoplus femomtus and Hippiscus tuherculatus, being at one side in 



