of Arenaceous Foraminifera. 207 



Thus the question is reduced to whether, under the circum- 

 stances mentioned, we are justified in concluding that the test 

 of Lituola canariensis as well as that of Bdelloidina aggregata 

 is t'mperforate because we cannot see the pores on the surface. 



I think not — and therefore maintain that it is better to adopt 

 the more probable view that they are 'perforate, and not " im- 

 perforate," although it may be beyond our power to demon- 

 strate the fact in all cases — moreover that the arenaceous 

 forms are so nearly allied to the vitreous ones respectively that 

 they should not be separated from them in classification. In 

 support of which I cannot do better than conclude these 

 observations with the following statement of one whose rare 

 amount of practical experience among both the marine and 

 freshwater Rhizopoda, together with his acute perception, 

 constitutes him a valuable authority. 



Dr. Wallich states : — " The inference which I venture to 

 draw from these facts is, that if due allowance be made for the 

 well-known proneness of the Protozoa, and notably of the 

 Foraminifera, to become modified by local or accidental con- 

 ditions, the Arenaceous character, taken by itself, ought not to 

 be regarded as indicative of new (i. e. genericallg distinct) 

 " Types " ; but merely of a change in the material of which 

 the shells are composed, resulting either from a deficiency in 

 the supply of Carbonate of Lime, or an excess of power in the 

 water of a particular locality to hold the Carbonate of Lime in 

 solution. And I submit that tliis view derives support from 

 the undeniable fact that the Arenaceous habit is to be seen in 

 various degrees of development in the following large series of 

 widely divergent Genera, namely, Lagena, Bigenerina, Quin- 

 quelocuUna^Textularia, Nodosariaj TJmgerina,I)iscorhina, and 

 even in Globigerina itself. Whilst the "rusty" colour said to be 

 characteristic of Lituola proper, not only pervades the entire 

 series in varying degrees, but presents itself also (as shall 

 hereafter be shown) amongst the Freshwater Testaceous 

 Rhizopods." {' Deep-sea Researches : Biology of Glohigerina.'' 

 By G. C. Wallich, M.D. &c., p. 62. Van Voorst, 1876.) 



I might here add that, being impressed with the idea that 

 the testaceous freshwater Rhizopods (many of which from 

 their rusty colour and arenaceous composition would, so far, be 

 taken for Lituolida if found in the sea) possess the power of 

 emitting sarcodic filaments from their surface for the purpose 

 of forming their tests, I have occasionally seen twitching 

 movements of the latter in the arenaceous forms, so like 

 those witnessed in the Dlatomaceffi that, being unable to 

 discover the cause of this in any other way, I have set it 

 down in both instances to the sudden separation of the free 



