KHIZOPODA LOBOSA:— ARCELLA, D1FFLUGIA. 



445 



expansions, insoluble particles which resist the digestive process 

 beincr got rid of in the like primitive fashion. 



333 The Amoeban, like the Actinophryan, type shows itself in 

 the Testaceous as well as in the naked form ; the commones ex- 

 amples of this being known under the names Arcella and Difflugia. 

 The body of the former is enclosed in a ' test 'composed of a horny 

 membrane, apparently resembling in constitution the cMine which 

 SyS solidity to the integuments of Insects ; it is usually discoidal 

 (Kg! 235, cf d) with one face flat and the other arched, the aper- 



Fig. 235. 



Testaceous forms of Amoeban Ettfeopodfl :-A, WWF**jr 

 formis; b, Mffiugia oblonga ; c, Arcella acuminata; d, A,ceua 

 dentata. 



ture being in the centre of the flat side ; and its surface is often 

 marked with a minute and regular pattern. The test oi Difflugia, 

 on the other hand, is more or less pitcher -shaped (tig. A&o, a , b;, 

 and is chiefly made up of minute particles of gravel, shell, &c., 

 cemented together. In each of these genera, the sarcode-body 

 resembles that of AmcBba in every essential particular ; the con- 

 trast between its large, distinct, lobose extensions (shown in rig. 

 235) and the ramifying and inosculating pseudopodia of bromm 

 (Ficr 232), bein- as obvious as the difference between an Amceba and 

 a UeberWinia. Amarine example of this type, remarkable alike tor 

 its extraordinary size and for the nature of its test has been 

 described byDr.O. Sandahl under the name AstrorhaahmicoLa. 

 Its form is lenticular, with irregular radiating extensions which 

 occasionally branch; the diameter of its central disk sometimes 

 attains l-5th of an inch; and its 'test' is composed of a spongy 

 substance intermingled with more solid particles.f this Uraei, 

 however, is not represented by any group of Calcareous-shelled 



* " Ofversight af Vet. Akad. Forhandl.," 1857, p. 299. 



t Frof LolS f, of Stockholm, to W hom the Author is indebted for 

 specimens of this remarkable organism, assures him that it •™™* 

 uncommon; so that it might probably be found on our own coast, tf 

 carefully looked-for. 



