AND THE LOWER ANIMALS. 195 



as the ciliated larva did. However, it very soon 

 abandons this wandering existence, attaches itself 

 once more, loses its vibratile cilia, employs its buccal 

 apparatus, which till then had been carefully folded 

 up, and soon elevated upon a new stem, which has 

 been developed from behind it, becomes the starting- 

 point of a new colony.* 



If we were writing a history of the Infusoria, we 

 should have much to say on the subjects of encystmentf 

 and co n j 'ligation. J These two phenomena are doubt- 



* In treating of the formation of the stems of Epistylis, most 

 authors use expressions which seem to imply that these stems have 

 no share in the vitality of the individuals. I believe, on the con- 

 trary, that the stems are living organisms. In support of this 

 view, I may mention that they are the seat of. phenomena which 

 cannot be explained by the adoption of any other opinion. Such 

 are : the increase in diameter as well as in length, the widening of 

 the base, the appearance of the central canal, described by Clapa- 

 rede and Lachmann, and which I myself have observed, &c. 



+ We apply the term Encystment to that act by which an 

 Infusorian surrounds itself with a solid shell secreted by itself, and 

 which places it beyond the control of external influences. Any 

 cause which brings about a result disagreeable to the animal, and 

 especially the evaporation of the drop of water in which it was 

 placed for examination, determines Encystment. Certain species 

 also appear to encyst themselves, in preparing to undergo spon- 

 taneous division. Stein especially investigated the phenomenon 

 from this point of view ; and finally it has been shown by Claparede 

 and Lachmann that certain species encyst themselves in order to 

 digest their captured prey more easily. Such is the case with 

 Amphileptus meleagris, which is nourished at the expense of Epis- 

 tylis, and whose curious mode of capturing its prey has been 

 described by the writers just alluded to. 



X Conjugation or Zygosis, discovered by Kolliker, and since in- 

 vestigated by most micrographers who have devoted themselves to 

 the study of Infusoria, is a phenomenon by which two, or a greater 

 number of individuals of the same species, appear to became fused, 

 so to speak, into one. M. Balbiani thinks that it is only an illusion 



