ORIGINS OF AGAMIC PATTERNS 



625 



velop, either irregularly scattered over the surface of the cytophore (Fig. 

 201, C) or covering the whole surface like an epithelium (Fig. 201, D). 

 The point of particular interest is that the polar pattern of the sperma- 

 tozoon develops radially to the cytophore, the motile tail, when present, 

 being peripheral (Fig. 201, C, D). The tubular nematode testis contains 

 a rhachis to which the cells remain attached up to a late stage of sperm 

 development, and the sperm axis is apparently the axis between free and 

 attached pole of the spermatocyte. 



Spermatozoa of many other forms, both invertebrate and vertebrate, 

 develop in bundles with axes parallel and heads imbedded in, or in contact 

 with, certain accessory cells. The spermatocysts, common among insects 



A B C 



Fig. 201, ^~Z>.— Sperm development in relation to a cytophore. A, spermatocytes and 

 part of cytoplasmic cytophore of earthworm (after Calkins, 1895); B, origin of cytophore of 

 the opisthobranch, Triopa clavigera, from degenerating cells (after O. S. Jensen, 1883); C, part 

 of cytophore and developing spermatozoa of the turbellarian, Plagiostomiim sulplmreum (after 

 Bohmig, 1891);/), cytophore of the annelid, Clitellio arenarius, containing degenerating nuclei 

 and showing a few of the spermatozoa which cover the whole surface (after O. S. Jensen, 1883). 



and the lower vertebrates, consist of spermatogenous cells inclosed in an 

 epithelial cyst; and spermatozoa develop parallel with heads toward, or 

 imbedded in, one of the cells of the cyst wall, usually of considerable 

 size, and believed to show evidence of secretory activity. How this par- 

 ticular cell is determined does not appear. The relation of spermatid pat- 

 tern to the basal or Sertoli cells appears very clearly in the mammalian 

 testis (Fig. 202, A, B). 



Cytophores and accessory cells to which the sperm axes are definitely 

 related have commonly been regarded as nutritive in function; and cases 

 like Figure 202, A and J5, have suggested the possibility of a tactic or 

 tropistic reaction of the spermatid to the Sertoli cell. But the question 

 arises whether the observed relations represent orientation of an axiate 

 pattern already determined, that is, a tropism in the strict sense, or de- 



