196 0. P. Bellinger. 



glass. PI. Ill, Fig. 2, shows the form the alveoli took. They are 

 seen to be in the angles of the crossed threads, and their general 

 arrangement is governed by the fibers. Another preparation was 

 made in which no threads were placed. PL III, Fig. 3, shows the 

 form of the alveoli in this case. PL III, Fig. 4, is the protoplasm of 

 Actinosphaerium. It is evident that Figs. 2 and 4 are structurally 

 alike, and one is convinced that there is fibrillar structure present in 

 the protoplasm of Actinosphaerium, which controls the arrangement 

 of the alveoli. The arrangement of alveoli in definite lines was 

 often remarked upon by Biitschli. This definite arrangement finds 

 an explanation in the above observations. Protoplasm, then, may be 

 a mixture of fibrillae with foams, the arrangement of the alveoli 

 being governed by the fibrillae. 



. So far as I know, there is nothing in this hypothesis that is contra- 

 dictory to what we know. On the other hand, it would explain the 

 presence of alveoli where a reticulum is demanded. It remains for 

 investigation to show how far this explanation holds good. The 

 above observations tend to strongly support it. In a later section 

 other evidence will be adduced. 



Probably more interest attaches to the work on the pseudopods 

 than to that on the body of the animal. As mentioned above, the 

 pscudopod has an axil filament that has generally been supposed to 

 be simply a supporting mechanism. This filament runs through the 

 ectosarc and ends near a nucleus in the endosarc. It is usually fig- 

 ured as if it were perfectly homogeneous (Fig. 8), but according to 

 this conception it is difficult to see how it is formed and how, under 

 stimuli, it is dravm into the body. 



While studying the pseudopods of Actinosphaerium to determine 

 the effects of different reagents it was noticed that the axil filament 

 was almost always more or less fibrillar. Following out this sugges- 

 tion, I made a careful study of j)seudopodia killed in 2 per cent, 

 osmic acid. By teasing such specimens, the fibrillar nature of the 

 axil thread becomes quite distinct. (PL III, Figs. 5, 6, 7, 8.) 

 Although it was difficult to trace the relations of these fibrillae inside 

 the body, examples were found which seemed to indicate that they, 

 in part at least, branch out into the meshwork of the trabeculae. 



