586 THE AMERICAN NATURALIST. [VOL. XXXVIII. 



structures are thickenings of the outer plasma membrane 

 (hautschicht) and opposed to this Timberlake's account for Hydro- 

 dictyon in which the blepharoplast is considered as a structure 

 independent of the plasma membrane although lying in contact 

 with it. It must be apparent that the results of Timberlake 

 are in essential agreement with the events of spermatogenesis 

 in the pteridophytes and gymnosperms while those of Stras- 

 burger introduce new elements in giving to the plasma mem- 

 brane the functions of forming a blepharoplast. The process of 

 spore formation in the ascus must also be considered in this con- 

 nection for in that sporangium a centrosphere associated with 

 each nucleus develops numerous fibrillse that resemble so much 

 a cluster of cilia as to suggest at once a blepharoplast-like struc- 

 ture, but this centrosphere of course is an important factor in 

 spindle formation during the mitoses in the ascus. Indeed we 

 may well ask for further studies in spermatogenesis and zoospore 

 formation before we can expect a solution of the problem of the 

 blepharoplast. 



Comparisons have been made between the sperms of animals 

 and plants, and some authors (e. g. Wilson : oo, p. 175, Belajeff 

 '9/c) consider the two cells in essential agreement as to structure 

 and development. However these views rest on the assumption 

 that the blepharoplast is truly the homologue of a centrosome. 

 It seems to be established that the locomotor apparatus of the 

 animal spermatozoon is derived chiefly from one or more centro- 

 somes, generally with the co-operation of archoplasm (idiozome, 

 Nebenkern) present in some form near the nucleus. It is true 

 that in plants the locomotor apparatus is derived from kinoplasm 

 which as we pointed out in Sections I and II corresponds closely 

 to the archoplasm of Boveri, but this is very far from implying 

 that structures formed by the archoplasm and kinoplasm respec- 

 tively need be homologous. Indeed both archoplasm and kino- 

 plasm are distinguished by their physiological activities rather 

 than by their morphological manifestations which are too various 

 to allow of close genetic relationships. Therefore it seems far 

 from established that spermatogenesis in plants is along the 

 same lines as in animals, especially since the weight of evidence 

 at present indicates that the blepharoplast is not a centrosome. 



