PROTOZOA. 167 



but at night these tiny beings light up the ocean with 

 myriads of lamps, whose phosphorescent property is 

 yet a profound mystery. 



The Cercomonady an animal- 

 cule, with a long flagellum at 

 each end, is noted for the thor- 

 ough investigations made by 

 Messrs. Dollinger and Drysdale. 

 These gentlemen found it would 

 increase for several days by fis- 



9 FIG. 71. Noctiluca miliaris. 



sion. Then it would lose the 



flagellae and assume an amoeboid form. Two of these 

 amoebiform Cercomonads would conjugate and become 

 encysted, and the rupture of the cyst gives exit to mi- 

 nute germs, which grow into the original parent form. 

 A temperature of 150 F. sufficed to destroy the adult 

 forms, but at 300 F. the germs still lived and devel- 

 oped. This latter fact makes strongly against the theory 

 of spontaneous generation. 



6. SPONGES, (Spongida.) What we familiarly call a 

 sponge is but the skeleton of a colony of Protozoa. In 

 this class a number of bioplasts, whose individuality is 

 still almost if not complete, are united together, sup- 

 ported on a skeleton of horny, silicious, or calcareous 

 fibers united so as to form a net-work of tubes. 



In a living sponge currents of fluid set in through 

 minute pores on the surface, and come out in large 

 streams through the larger apertures, (oscula^) These 

 currents are kept up by the cilia connected with the bio- 

 plasmic masses which line the canals and cover the 

 skeleton. By means of these currents particles of food 



