THE SIMPLER ORGANISMS 715 



shaped form (whence they are called pseudo-navicellae} and 

 these are liberated by the rupturing of the containing wall. 

 The spores are scattered among the herbage and may 

 readily be eaten by another grasshopper in the spring; 

 and if so fortunate (for therein lies their only chance of 

 further development) , they repeat the cycle just outlined. 



The deviations from the normal course of protozoan life 

 in gregarines seems to be due to their peculiar parasitic 

 habits. A long period of uninterrupted growth is followed 

 by rapid and extensive cell division, reducing the size again, 

 first to that of normal gametes, and after fertilization, 

 reducing it again to that of the spores.) 



Study 16. Observations on reproduction among the simpler 

 organisms. 



Materials needed: For fusion between cells of ordinary 

 size, conjugating Spirogyra, or any of the Conjugatae 

 among the algae, fresh or preserved (temporary and partial 

 conjugation may often be seen in Paramoecium and its allies 

 among the ciliate protozoans, but the details are not easily 

 followed by a beginner) . 



For gametes, one of which is of moderately reduced size 

 and of increased activity, preserved material in Vorticel- 

 lidae, or, better, in any of the algae, among which this is of 

 frequent occurrence. 



For fusion between cells both of which are of greatly 

 reduced size, fresh and preserved gregarine material. For 

 fresh material, up to the beginning of the dividing process, 

 open the stomachs of freshly collected grasshoppers (the 

 head may be snipped off : the body wall slit open ; the ali- 

 mentary canal lifted out entire and freed from extraneous 

 organs and fat, the stomach wall, opened by a longitudinal 

 slit, either with fine scissors or with a very sharp scalpel: 

 the walls will open by the contraction of their own muscles. 



