132 AnCHKGONIATES. 



(Fig. 52, A). Along the outer edge of 'the cytoplasmic band extends 

 the blepharoplast as a thread or narrow band from which the cilia arise. 

 The blepharoplast reaches almost or quite to the anterior extremity of 

 the cytoplasmic part, but it cannot be traced farther back than the 

 posterior extremity of the cytoplasmic part, although it may extend 

 some distance farther as a delicate thread closely applied to the nucleus. 

 The blepharoplast is broadest at its anterior end, where it seems to be 

 not perfectly flat, but curved, appearing as a double line, or in cross 

 section as a shallow U. It is, however, very small, so that the exact 

 shape is difficult to determine with certainty. As already stated, it 

 becomes a very delicate thread at the posterior end which is brought 



FIG. $3. Two mature spermatozoids drawn from specimens that were fixed and stained 



upon the slide a few minutes after their escape from the antheridium. 



A, Onoclea strutkiopteris ; B, Marsilia vestita. 



close to the nucleus by the narrowing of the cytoplasmic band. It is 

 probably for this reason that it cannot be traced after coming into con- 

 tact with the nucleus. There is nothing to indicate that the blepharo- 

 plast extends to the posterior end of the nucleus. The cilia begin 

 at a short distance from the anterior end, and extend backward about 

 two and one-half or three turns. Their length equals or even exceeds 

 that of the spermatozoid when extended. 



Judging from Belajeff's figure of a mature spermatozoid, it would 

 seem that the cytoplasm envelops the entire nuclear portion, but in my 

 own preparations, which were made by killing and staining the sper- 

 matozoids upon the slide after they had escaped from the antheridium, 

 no cytoplasmic mantle was seen to surround the posterior part of the 

 nucleus. Thorn ('99) states also that the whole nucleus is surrounded 

 by a cytoplasmic envelope. It is possible, of course, that the plasma 

 membrane, or even a thin layer of cytoplasm, may envelop the nuclear 

 portion. The nucleus usually appears homogeneous in structure, but 



