PEOTOPLASTA— THE LOBOSE PEOTOPLASTS. 29 



assure comparative uniformity of character in the shape, size, and consti- 

 tution of the shell, just as buds of the same plant ordinarily assure the 

 same varieties of flowers and fruit. On the other hand, reproduction of 

 the Rhizopods from germs or spores would probably furnish a partial 

 explanation of the multitudinous varieties of form. 



The naked Protoplasts, as represented by species of Amoeba, etc., at 

 times which are apparently related with circumstances unfavorable to 

 activity, even of an opposite character, as extremes of temperature, cold 

 or heat, assume a condition of complete quiescence, reminding one of the 

 winter or summer sleep of higher animals. The condition is preceded by 

 retirement into the deeper part of the ooze in which these lowly creatures 

 live, or by concealment in dirt and other materials accumulated around and 

 adherent to them. Contracted into a globular form, they are purged of all 

 remains of food and other materials, such as sand, etc., swallowed with the 

 former. They then become gradually invested with a structureless mem- 

 brane consisting of one or several layers, apparently the product of exuda- 

 tion and coagulation of a portion of the protoplasm of the sarcode mass 

 of the body. In this encysted condition, the Protoplast remains an indefi- 

 nite period, and perhaps usually undergoes transformation into reproductive 

 germs or spores. Often, however, if the circumstances are changed for one 

 favorable to activity, the creature bursts its envelope and creeps forth to 

 feed in the ordinary manner, as if it had been passing a time in sleep. 



The shell-covered Protoplasts are frequently found with the sarcode 

 mass contracted into a ball commonly defined by a membrane of variable 

 thickness, and apparently due to the coagulation or condensation of the 

 ectosarc, or of an exterior more clear and homogeneous layer of the soft 

 structure. In the formation of these quiescent balls, they are purged of all 

 remains of the food which is often seen occupying the space between the 

 ball and the mouth of the shell. Frequently, also, in the quiescent or 

 encysted condition of the sarcode, the mouth of the shell is closed by an 

 operculum apparently formed by the accumulation of successive layers of 

 matters discharged from the sarcode ball. 



The encysted ball of the shell-covered Protoplasts in many instances 

 appears to be resolved into globules, or coarse granules of nearly uniform 

 size, which are probably to be viewed as germs or spores. 



From the researches of Mr. Carter* it would appear that in Amoeba 



"Annals and Magazine of Natural History, xviii, 1856, p. 226. 



