1903.] NATURAL SCIENCES OF PHILADELPHIA. 639 



brane generally about 20 microns thick, but often much thicker. This 

 variation in the thickness of the membrane appears to be due to the 

 quantity of extraneous matter which gets tangled within it as it forms. 

 It was noticeable that the thin walls were clear and clean, while the 

 thick walls were very much matted with substance from the host's 

 intestine. Dehiscence by a slit which, in the cases observed, extended 

 only part way around the cyst. Sporulation partial. Maturation 

 period 8 days. May 17-25, 1903. 



Spores: Length 12^ microns; breadth 7^ microns. Two coated, the 

 epispore of some consistent gelatinous substance; the endospore 

 cuticular. The latter presents an elliptical profile, with slightly pro- 

 truding ends, whereas the epispore is pulled out considerably at the 

 ends, and somewhat irregular in outline. Sporoplasm hyaline, with a 

 central mass of granules. The spores adhere in files and masses. 



Gregarina achetaeabbreviatae Leidy. 



Gregarina achekeahhreviatce Leidy (1S53), p. 238, PI. 11, figs. 33, 34. 

 Gregarina a'chetoEabbreviaice Crawley (1903), p. 45, PL 3, figs. 34, 35. 



To the previous notices of this species add : 



Cysts: Spherical, enclosed in a more or less irregularly shaped thick 

 gelatinous envelope. Diameter of the cyst mass, without the gelati- 

 nous envelope, 225 microns. Cuticular membrane 6-8 microns thick. 

 The gelatinous envelope varied in thickness from 100-300 microns. De- 

 hiscence by sporoducts, 2-5 in number, reaching a length of 1000 

 microns. Prior to evagination, the situation of the sporoducts is 

 plainly indicated by the appearance around the periphery of the cyst 

 of dense discoid masses, yellowish in color. This yellowish color is 

 due to the presence of an oil, which, when the sporoducts evert, appears 

 to be within the substance of their walls, and not within their lumina. 

 The two cysts obtained everted their sporoducts one day after removal 

 from the host intestine. 



Spores: Unknown, for, rather curiously, although the sporoducts 

 everted, no spores appeared. 



The list of the polycystid gregarines of the United States, revised to 

 date, is as follows: 



Fam. GREGARINID^. 



1. Gregarina blattarum Sieb. 



2. Gregarina ACHET^ABBREViATiB Leidy. 



3. Gregarina passalicornuti Leidy. 



4. Gregarina calverti Crawley. 



5. GiGADucTus parvus Crawley. 



