THE EGG-PHASE OF ANIMALS. 31 



plicity of the lowest animate forms, the Amoeba, Difflugia, and 

 others like them, let us turn to a consideration of the lowest con- 

 dition of life in which any animal, whether high or low, can 

 exist. I mean the egg-state ! Let us compare this preliminary, 

 scarcely organized, low form or state of life which we find in the 

 egg, with these gum-drop like beings, as I have called the 

 Amoebas, Difflugias, &c. In the first place we must consider 

 what an egg is, and under what conditions it originates and 

 exists. 



Originally, that is when beginning to form, an egg is a very 

 minute aggregation of fluid matter, more simple even than the 

 Vibrios and Bacteriums of the sealed-flask experiments of Dr. 

 Wyman, and yet this fluid is gradually transformed into mi- 

 nute granular bodies, the yolk-granules so called, and these in their 

 turn eventually become cells, and by combining form a living, 

 sentient being. Now when we turn to the lowest animals, such 

 as Amreba, Difflugia, Rotalia, &c., we find among them those 

 which are nearly or fully as simple as the eggs 

 which they themselves lay. In the latter instance, 

 the egg, in order to become an adult, merely 

 changes its form without developing into an ap- 

 preciably more complicated state. Those un- 

 doubted animal infusoria, such as Paramecium 

 (fig. 96), Stentor (fig. 30), Epistylis (fig. 95), 

 Pleuronema (fig. 90), &c., arise from 

 eggs which are not such as might 

 answer fully to the theoretical egg of 

 physiologists. Balbiani (Journ. Phy- 

 10 siol., 1861, IV.) found that the egg Fig. n. 



of Spirostomum (fig. 10, A) and Stentor (fig. 11) is a mere 

 cell, without any other sign of the characteristic nucleus-like 

 Fig. 10. Spirostomum teres. Clap. 150 diam. View of the lower side, showing 

 the narrow oblique furrow which passes from the mouth, m, to the end of the 

 body ; c, tubular contractile vesicle; e, eggs. A, one of these eggs more highly 

 magnified. From Balbiani. 



Fi. 11. The e< of Stentor cceruleum. Ehr. 500 diam. The central clear 



^D CO 



space is all that represents the germinal vesicle. From Balbiani. 



