JtfLT 31, 1914] 



SCIENCE 



175 



if present at all being reduced to a thin film. 

 If placed in water immediately after being 

 discharged from the host, the cysts remain un- 

 changed in external appearance for 4 days or 

 more. After about 5 days the formation of 

 sporocysts has progressed to such an extent 

 that the cysts begin to turn gray, changing 

 gradually to jet black in the next 2 or 3 days. 

 Shortly after reaching the jet-black stage the 

 cysts dehisce by simple rupture, discharging 

 the long chains of ovoid sporocysts. Ten days 

 usually elapsed between the time the cyst left 

 the host and dehiscence, and no cyst examined 

 dehisced in less than 8 days. 



By starving the hosts it was found that the 

 cysts were discharged in numbers almost free 

 from excrement, and that such fluid excrement 

 as did accompany the cysts dried rapidly, 

 leaving the naked cysts glued to the glass tubes 

 in which the hosts were confined. On Septem- 

 ber 23, 1913, several Eleodes sp. which had 

 been starved for five days were placed in clean 

 test tubes and over fifty cysts collected. The 

 fluid excrement surrounding these dried in 

 less than three hours, leaving the naked cysts 

 adhering to the walls of the tubes. The beetles 

 were removed and the tubes loosely plugged 

 with cheese cloth. After plugging the tubes 

 they were returned to the rack and allowed to 

 remain undisturbed for 138 days. During 

 this time they were in the light that came in 

 through a north window, but not in direct 

 sunlight, and were subjected to severe drying, 

 as the room in which they were kept was 

 heated with dry air, which together with the 

 naturally dry air of Colorado dehydrated the 

 cysts to such an extent that they shriveled and 

 fell to the bottom of the tubes. On January 

 23, 1914, such cysts as had fallen to the 

 bottoms of the tubes were removed and exam- 

 ined. All were still white, showing that the 

 last stages of sporocyst formation had not 

 been reached, and all were much shriveled and 

 wrinkled, being reduced to half or less of their 

 original volume. The dry cysts were then 

 placed in water and after twenty-four hours' 

 soaking they resumed their original spherical 

 shape, still remaining white. By the end of 

 the second twenty-four hours in water they 



had turned dark gray, and on the third day 

 all were jet black, some having dehisced the 

 long chains of ovoid sporocysts. From the 

 time of discharge from the host to dehiscence 

 these cysts were in fluid excrement for less 

 than three hours, in dry air for 138 days and 

 in water for less than three days. During 

 the period of drying they did not lose their 

 vitality and sporocyst formation was not com- 

 pleted. That internal changes had taken place 

 in spite of the dry air is suggested by the rapid 

 completion of sporocyst formation when the 

 cysts were placed in water, dehiscence taking 

 place in three days as compared with matura- 

 tion period of ten days required by cysts taken 

 directly from fresh excrement and placed in 

 water. 



This ability of the cysts of Stylocephalus 

 giganteus to withstand a certain desiccation is 

 perhaps an important factor in the distribu- 

 tion of this parasite which is so generally 

 successful in eastern Colorado. Two stages at 

 least, the cyst and the sporocyst, and possibly 

 a third, the sporozoite, must be considered as 

 distributional stages, comparable to some ex- 

 tent to those stages of many parasites which 

 are passed in the secondary hosts. Each cyst 

 of Stylocephalus giganteus produces an enor- 

 mous number of sporocysts, which, as in most 

 species of gregarines, are well protected by 

 tough coats, and from the standpoint of species 

 distribution both the number of sporocysts 

 and their tough, protective coats are presum- 

 ably positive factors in increasing the chances 

 of this species being talien into the alimentary 

 canal of many hosts. If the cyst be destroyed 

 the type of sporocyst is of no importance, and 

 cysts are produced in relatively small num- 

 bers, since each represents a fusion of two 

 adult gregarines. It is then essential to the 

 gregarine species that the cyst be able to with- 

 stand the unfavorable conditions of the en- 

 vironment in the habitat of the host species 

 until sporocysts may be formed. This is ac- 

 complished in some species as Gregarina 

 hlattarum Siebold of the cockroach and Greg- 

 arina rigida (Hall) of various species of 

 grasshoppers, by the thick gelatinous envelope 

 surrounding the cyst. This envelope when 



