642 PROCEEDINGS OF THE ACADEMY OF [Oct., 



reached the outside world. In the case of this species, I obtained quite 

 a number of cysts, all of which went through the process in approxi- 

 mately the same time. It is also worthy of note that the spores of 

 these two species mature rapidly. Those of Gigaductus parvus showed 

 differentiation into sporozoites as soon as they were ejected from the 

 cysts. Gregarina calverti was a trifle slower, but the sporozoites were 

 to be detected within half a day after dehiscence. 



Cnemidospora spiroboli, Adinocephalus harpali and Acutispora macro- 

 cephala showed periods of from 8 to 10 days. Of these three species, 

 the cysts of the first two dehisce by simple rupture, that of the third 

 by the formation of a pseudocyst. A . dujardini, which was thirty days 

 maturing, also dehisces by simple rupture. Although the facts are 

 few, they point to the conclusion that when dehiscence is by rupture, 

 maturation is a slower process than when sporoducts are formed. 

 Further, the spores of these last-named species did not, for several 

 days, show any differentiation into sporozoites. Of course, temperature 

 is a factor in determining the time, but the cysts of A. harpali were 

 exposed to exactly the same conditions as those of the two species of 

 Gregarina and of Gigaductus par-vus. 



IV. 



The cysts of Acidispora macrocephala present some points of interest. 

 They were obtained on May 10, from a specimen of Lithobius forficatus, 

 sent me from Raleigh, N. C. At this time they were perfectly spherical, 

 420 microns in diameter, with a cuticular wall 40 microns thick. There 

 were several cysts in the intestine of the myriapod, all about the same 

 size, and of these two matured. On May 18, the appearance presented 

 is shown in PI. XXX, fig. 4. The protective membrane was still clear 

 and the cyst proper still very dense. One hemisphere was now con- 

 siderably larger than the other, and on the surface of this larger hemi- 

 sphere there were a few indistinct furrows. These fuiTows do not ap- 

 pear to possess any especial signification, although they may be taken 

 as a sign that the cyst is nearly mature. Two days later. May 20, the 

 cyst presented quite a different aspect. The protective membrane had 

 swollen greatly and was evidently undergoing a rapid decay (fig. 5)- 

 At one pole, the upper in the figure, it was much thinner than elsewhere, 

 and it was from this pole that the spores eventually emerged. Within 

 lay the cyst mass, now having the form of an acorn, and consisting of 

 an ellipsoidal body, around one end of which was a thick ring. At the 

 free end of this ellipsoidal body, which is the spore mass, a definitive 

 membrane could be seen. This membrane, although presenting a 



