238 THE AMERICAN NATURALIST. [Vol. XXXIX. 



sexual act (fertilization) but there remains for consideration the 

 behavior of certain cytoplasmic elements introduced into the 

 sexually formed cell, especially chromatophores and the blephar- 

 oplast. Since the blepharoplast bears a very close resemblance 

 to the middle piece of the animal spermatozoon, which some- 

 times becomes a centrosome in the animal egg, a critical com- 

 parison of the behavior of these two structures during fertiliza- 

 tion is full of interest. 



Except for certain accounts of Spirogyra, to be described in 

 the next paragraph, investigators agree that the chromatophores 

 or plastids of gametes never fuse in the sexually formed spore. 

 Plastids have not been found in the sperms of the gymnosperms, 

 pteridophytes, nor bryophytes. The sperms of some algae also 

 appear quite colorless at maturity but careful examinations have 

 shown in a number of forms a very small chromatophore in the 

 early stages of development. Other less highly differentiated 

 sperms are known to have chromatophores {e. g., Sphseroplea, 

 Cutleria, Volvox). Both gametes in the isogamous types of 

 sexuality among the algas always have chromatophores or plas- 

 tids. These have been followed in detail through stages of fer- 

 tilization in Ectocarpus by Berthold ('81) and Oltmanns ('99), 

 and in Scytosiphon by Kuckuck ('98) where it is evident that 

 they do not unite and there is no reason for believing that differ- 

 ent conditions obtain among any of the lower forms such as 

 Ulothrix, Cladophora, Hydrodictyon, etc., although detailed 

 observations are greatly lacking on this point, chiefly because 

 the conjugating cells are generally very small. 



Early accounts of the formation of the zygospore of Spirogyra 

 have reported some form of union of the chlorophyll bands of 

 the two gametes. The last work upon the subject, Chmielewski 

 ('90a), reviews the results of previous investigators and gives a 

 detailed account of a species of Rynchonema (Spirogyra). 

 Chmielewski claims that the chromatophore of the gamete (male) 

 that passes over into the other cell (female) becomes disorgan- 

 ized as the zygospore develops. While the chlorophyll band of 

 the female cell retains much of its color, that from the male 

 becomes yellowish and breaks up into fragments which become 

 scattered in the zygospore and finally break down. This inter- 



