238 THE AMERICAN NATURALIST. . [Vor. 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 
tothe 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 algz 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., Sphzeroplea, 
Cutleria, Volvox). Both gametes in the isogamous types of 
sexuality among the algae always have chromatophores or plas- 
tids. These have been followed in detail through stages of fer- 
tilization in Ectocarpus by Berthold ('8 1) 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- 
