192 CALIFORNIA ACADEMY OF SCIENCES. 



ment of the spermatozoids. and this point was only ob- 

 served in a very casual way. Nothing was observed, 

 however, which pointed to anything peculiar in their 

 origin. As in other cases observed, the body of the 

 spermatozoid is derived from the nucleus of the sperm- 

 cell by its direct change in form. It tirst contracts on 

 one side and forms a thick curved band (pi. in, fig. 21) 

 which then lengthens out and becomes thinner and many 

 times coiled until it has assumed the corkscrew form of 

 the full-grown spermatozoid. The cilia and the vesicle 

 which is attached to the hinder end are derived from the 

 cytoplasm. 



When the antheridia are ripe, which ordinarily takes 

 place in about twelve or sixteen hours after the spores are 

 placed in water, the cells forming the walls become very 

 much distended by the rapid absorption of water, and in 

 consequence of the pressure from within the exospore 

 breaks open along the lines of the three radiating ridges 

 at the apex, and the upper swollen cells of the antheridia 

 protrude through the opening. Finally the peripheral 

 cells are torn apart, and the sperm-cells with the con- 

 tained spermatozoids are discharged. The walls of the 

 sperm-cells are soon completely dissolved and the sper- 

 matozoids are thus set free. 



The spermatozoids of Marsilia are distinguished from 

 all others by the great number of coils in the spiral body. 

 In the species under consideration there may be thirteen 

 or fourteen. In the active condition (pi. in, fig. 22, a) 

 the coils are close together and the lower coils much 

 wider. When the movements begin to slacken, or when 

 the body is held in the mucilaginous matter about the 

 macrospore, the spiral often becomes much elongated 

 (pi. Ill, fig. 22, b). The very numerous long cilia are at- 

 tached mainly to the lower coils, and the upper pointed 



