6i8 PATTERNS AND PROBLEMS OF DEVELOPMENT 



uals originate as ectoplasmic fields in definite relation to the parental pat- 

 tern, and their orientation is presumably determined by it. 



In many of these protozoan forms more or less morphological dediffer- 

 entiation occurs in connection with division, and the characteristic asym- 

 metries redevelop in the new cell generation ; but the essential physiologi- 

 cal factors of pattern evidently persist, or originate within the parental 

 pattern in an orientation with respect to it which is definite and char- 

 acteristic for the species. That the various asymmetries are in some way 

 associated with the specifically different physicochemical constitutions 

 of the species-protoplasms seems beyond question. Various suggestions 

 and possibilities will be considered in a later section after some other asym- 

 metries of unicellular individuals have been noted. 



PATTERNS OF PLANT AND ANIMAL SPERMS 



Antherozooids, and spermatozoids of plants and spermatozoa of ani- 

 mals show great variety of morphological pattern. A heteropolar longi- 

 tudinal pattern is almost always present; in some forms there is complete, 

 or almost complete, radial symmetry about the axis of this pattern; in 

 others a spiral pattern develops, either in the whole individual or in some 

 part of it; and in still others other asymmetries characteristic for the 

 species appear. 



ANTHEROZOOIDS AND SPERMATOZOIDS OF PLANTS 



The sperms of many algae are biflagellate forms similar to the zoospores 

 in general pattern (see Fig. i86. A, C) but often smaller than zoospores 

 of the same species. In some forms there appear to be gradations in size 

 and behavior as zoospores or gametes. The pigmented spot or stigma is 

 asymmetrical in position in forms with terminal flagella, as in similar 

 zoospores (Fig. i86. A); and in forms with lateral flagella both flagella 

 and stigma are asymmetrical in position (Fig. i86, C). As in the case of 

 zoospores, the question how these patterns originate or whether they show 

 relation to any particular factors is unanswered (see pp. 601-3). 



The antherozooid or spermatozoid of Chara is an elongated, spirally 

 coiled biflagellate cell (Fig. ig6, A). The antheridial filament consists of 

 a single series of flattened cells, each of which metamorphoses into a single 

 antherozooid. After the final division the nucleus moves toward the side 

 wall; the blepharoplast appears adjoining the cell surface toward the base 

 of the filament, elongates, and becomes spirally coiled; and elongation and 

 spiral coiling of the nucleus follow, the axis about which the spiral develops 



