220 Dr. Wallich 07i the Amoeba. 



" The pushing forward of the more fluid constituents is 

 effected bj the action of a pressure on the opposite side ; this 

 IS produced hy the extremest layer at this part acquiring a 

 tougher consistency bj extraction of water. The latter is 

 widened during the flow of the Amoeba at the posterior end by 

 all sorts of processes, lobes, hairs, &c., which often give the 

 Amoeba a peculiar aspect, and have led to the establishment of 

 distinct species. The sarcode here becomes so tough that as 

 the Amoeba hastens forward it draws into threads ^ if the ex- 

 pression may be allowed. If the direction of movement is 

 reversed, the previous posterior extremity begins to flow, a7id 

 the most tenacious 'protoplasm occurs on the opj^osite side^ — 

 Ibid. p. 115. 



" Gruber is of opinion that the discrimination of zones of 

 difierent kinds of protoplasm is due to a misunderstanding ; 

 the Amoebic body always consists of a single mass of proto- 

 plasm in which the various contents are suspended ; when the 

 plasma is fluid the contents are well distributed^ but lohen it is 

 ■firmer they do not mix so easily mith it ; this is the cause of 

 the appearance of a hyaline ectoplasm and a granular endo- 

 plasm. The only differentiation in the body of an Amoeba 

 obtains at the outermost periphery ^ where the protoplasm, clearly 

 from contact with water , is converted into an invisible cuticula- 

 liJce layer, which disappears during the outpushing of the 

 pseudopodia, and can be remade.'''' — Epitome of Dr. Gruber's 

 paper in the Journ. Koy. Micr. Soc. for April 1884 (p. 260), 

 the paper itself having been published in Zeitschr. f. wiss. 

 Zool. xli. 1884, pp. 186-225. 



" The diagnosis of an Amoeba must be based on its average 

 size, the consistency of the protoplasm, and the movements 

 therein conditioned, as well as on the characters of its contents, 

 such as vacuoles, granules, crystals, but chiefly on the number, 

 size, and structure of the nuclei. Five of the species described 

 in the present essay are multinuclear, and it is proved how 

 definitely the nuclei are distinguished from one another, and 

 with what certainty one can conclude from external characters 

 on the structure of the nucleus, and vice versa. Thence results 

 the remarkable fact that two very similar species of Amc^ba 

 may have very differently formed nuclei, and that in forms 

 wdiich are externally very different the nuclei may be quite 

 similar. In any case the number of the different forms of 

 nuclei is much more important than has hitherto been sup- 

 posed."— /^/^. pp. 260-1. 



The species lately described by Leidy and found by 

 Gruber in Europe confirm the doctrine that the freshwater 

 Khizopods are cosmopolitan organisms. 



