66 



MEMOIRS OF THE UNIVERSITY OP CALIFORNIA 



to that species, its size being considerably greater and its form quite unlike the 

 typical houiJ a (fig. Q, 5). His Gyiu nodi niton fi(sus (^ Gyrodiuinm falcafiim), 

 sho%YU in his figure 81, plate 25, is still another species, probably representing 

 a secondary cyst stage comparable to that of G. lunula. Dogiel (1906) has 

 figured one large encysted Gymnodinkim in his figure 20, plate 1, which is also 

 not G. lunida, but quite evidently another distinct species. 



These facts and our own observations demonstrate a wide prevalence of 

 these temporarily to more permanently encysted stages in the Gpnnodiniidae, 

 and lead to the conclusion that a type of Life history similar to that shown for 



Fig. J. Blastodinium pruvoti Chatton. After Chatton (1906, figs. 1-5). 1. Paracalanus parvus (Claus), 

 containing three blastodiniums (par.) in the intestine. X 200. 2. Blastodinium pruvoti, showing circles of spines 

 around the body and two nuclei. X 400. 3. Division of the body into two parts, macrocyte (mac.) and microcyte 

 (mic). Division is taking place in the latter. 4. Further development of both macrocyte and microcyte. 

 5. Gymnodinium-like form developed from the microcyte. X 500. 



Gymnodinium lunida is to be expected for all the members of this group. It 

 is probably a much shorter stage and also much less frequent than that of the 

 vegetative motile phase, and hence is less coimnon. The pyrocystis stage may 

 also be the resting period for the organism, and may require certain conditions 

 or seasons for its production. The whole question is still an open one, however, 

 and requires further investigation for the solution of its many difficulties. 



Effects of Paeasitis:m ox Life Cycle. — Still further complexity has been 

 introduced into the life cycle with the adoption of a parasitic mode of life by 

 one group of the GjTnnodinioidae, the Blastodiniidae. Our knowledge of these 



