1903.] NATURAL SCIENCES OF PHILADELPHIA. 43 



the immunity is probably due to the inabiUty of a gTCgarine sporozoite 

 to get into the cells. 



The 32 specimens of Polydesmus examined were some from Wyncote 

 and some from Raleigh, N. C. Polydesmus is infected by two greg- 

 arines, Gregarina polydesmivirginiensis and Amphoroides jontarice. Of 

 these, both were present in 14 hosts, G. polydesmivirgimensis alone in 

 five and A. fontarice alone in seven. The Diplopods from one region 

 were about as frequently parasitized as from the other, but G. polydes- 

 mivirginiensis was present oftener and in larger numbers in the animals 

 from Wyncote than in those from Raleigh, while the reverse was true in 

 the case of A. fontarice. It is for this reason that the latter, although a 

 frequent parasite of Polydesmus. has been named for Fontaria. Where 

 two gregarines parasitize a given host, it is generally found that one 

 occurs far more frequently than the other. The more frequent para- 

 site is spoken of as the primary, the other as the secondary. Usually- 

 also, the primary parasite of one host is the secondary of another. In 

 Pennsylvania, where Polydesmus is common and Fontaria does not 

 occur, the former, as stated above, is more often parasitized by G. poly- 

 desmivirginiensis than by A. fontarice. In North Carolina, where Fon- 

 taria is common, the more usual parasite of Polydesmus is A. fontarice. 

 This gregarine, furthermore, was present in great numbers in the two 

 individuals of Fontaria I was able to examine. It may therefore be 

 concluded that G. polydesmivirginiensis is the primary of Polydesmus, 

 while A. fontarice is the primary of Fontaria. 



In Polydesmus, G. polydesmivirginiensis was usually present in mod- 

 erate numbers, from 20 to 50, although occasionally there were only a 

 very few. On the other hand, A. fontarice ran to extremes. Some 

 millipedes would show only two or three gregarines, while in other cases 

 they were present by the hundreds. There were only a few, however, 

 in the animals taken at Wyncote. 



Of sixteen specimens of Lysiopetalum lactarium. six were parasitized. 

 Two gregarines occur, one a new species which I have named Gregarina 

 calverti, the other apparently StenopJwra juli. Both gregarines were 

 present in two hosts, G. calverti alone in three and S. jidi alone in one. 

 Thus the former species was present five times and the latter three. 

 G. calverti is therefore to be regarded as the primary parasite of Lysio- 

 petalum. 



This miUipede is found under stones in much dryer places than 

 Julus, Parajulus or Polydesmus, and it is somewhat solitary in habit. 

 It is thus easy to see why only a comparatively small percentage of 

 them is parasitized. G. calverti occurred in moderate numbers in all 



