970 SUMMARY OF CURRENT RESEARCHES RELATING TO 



(4) The ftpectjic distinctions of Amcebae are finally discussed. Tho 

 apparently simple protoplasmic body is in reality very heterogeneous. 

 The fine difi'erences between the species are far from passing phases, 

 but express constant protoplasmic qualities. 



Various Cyst-formations and Developmental History of Colpoda.* 

 — llcrr L. Ehumblcr Las investigated the life-history of this holotrichous 

 Infusoriau. In discussing the granular deposits on the endojilasm and 

 the metabolism of the Infusoria, he points out that the corpuscles are of 

 service in assimilation, as they convert the useful stuffs of the ingested 

 food into protoplasm. Assimilation is only effected with the aid of 

 water containing oxygen, and taken in from outside the body. This 

 traverses the clear zones of the assimilation-corpuscles, and after giving 

 up its oxygen, is driven to the exterior by the vacuole. These assimila- 

 tion-corpuscles give off their assimilated protoplasm for the purpose of 

 forming new parts, and for the further growth of the rest of the endo- 

 plasm. As the final product of metabolism, they excrete uric acid in 

 their interior, where they are gradually collected. The corpuscles are 

 finally destroyed. When this happens the outer protoplasmic zone of 

 the corpuscles is again given up to the eudoplasm, while the particles of 

 uric acid are passed to the exterior by the contractile vacuole. This 

 last is, therefore, both an excretory and a respiratory organ. In this 

 Infusorian, further, assimilation and respiration are united in one process. 



The cysts of Colpoda are of three kinds : dividing cysts, lasting cysts, 

 and spurocysts. The first of these is characterized by an orifice in its 

 wall, by the presence of nutrient spheres in the endoplasm, by the undis- 

 turbed pulsation of the vacuole, and by the process of division. The 

 lasting cyst has none of these characters. The sporocyst is distinguished 

 by being protected by two (sometimes three) envelopes ; the contents are 

 such that the primitive organization of the Colpoda can no longer be 

 recognized; the assimilation -corpuscles are broken up and their uric 

 acid excreted ; the sarcode, by the loss of the water, is condensed to an 

 eighth ; the nucleus is no longer apparent ; and the body-vyall itself is to 

 all appearance lost. 



These various cysts may, under certain circumstances, be converted 

 into one another, the dividing cyst becoming a lasting cyst or a sporocyst, 

 and the lasting cyst a sporocyst. The latter may be effected either by 

 the particles of uric acid from the assimilation-corpuscles and the watery 

 fluid being slowly expelled by the vacuole, or by both gradually passing 

 from all parts of the periphery of the body into the velar space. It is 

 clear that the sporocyst cannot be converted into any other kind of cyst, 

 if we reflect that the complete degeneration of the organization shows 

 that the animal has come to an end of its individual life. 



On the first appearance of the dividing cyst, its movement in more or 

 less straight lines is often broken by rotatory movement. I'he lastin^r 

 cyst moves rapidly across the field of vision, and the sporocyst still more 

 rapidly. The first has nutrient spheres within, the other two have ex- 

 pelltd them. While the gelatinous envelope is beintj excreted and hardens, 

 the dividing cyst rotates around the long axis of the body or remains at 

 rest, and the contractile vacuole is always at the same place, so that there 

 is an orifice in the wall of the cyst ; the other two forms rotate around 

 various axes, the vacuole appears at different points, and there is no 

 orifice in the cyst-wall. During and after the hardening of the cyst-wall 



• Zeitschr. f. Wiss. Zool., xlvi. (1888) pp. 5J9-601 (1 pi.). 



