8 BULLETIX 120, UNITED STATES NATIONAL MUSEUM. 



each ciliiim arises from a spherical" basal granule which lies just 

 beneath the pellicle. 



The pellicle is a fairly firm membrane of visible thickness. To 

 its tension is probably clue the shape of the body. The pellicle 

 bears longitudinal and slightly spiral grooves which are demon- 

 strated only with difficulty. In these grooves are set the chief rows 

 of cilia. If the accessory rows of cilia are set in grooves at all, 

 these seem to be less developed than those which bear the main 

 rows of cilia. 



Immediately beneath the pellicle is an outer layer of ectosarc 

 Avhich bears no clearly visible alveoles, but seems finely granular. 

 In figure 3 it is shown unstippled. It is in this granular layer 

 that the basal granules of the cilia lie. The basal granules in each 

 longitudinal row are united by an extremely delicate longitudinal 

 thread. Similarly the basal granules of adjacent rows seem to be 

 connected transversely by very delicate fibrillae, though the ap- 

 pearance is more vague and less sharply defined. In this way is 

 formed a network of delicate fibrillae with squarish meshes and 

 bearing at each (?) node a basal granule of a cilium. This fibrillar 

 network probably serves the nervous function of coordination of 

 the movements of the cilia and may be regarded as a rudimentary 

 nervous system comparable to the much more highly developed 

 nervous system of many Ciliates and Flagellates, so finely described 

 by Kofoid and his pupils. IS'o nervous centers have been observed in 

 connection with this network in any species of Opalinid. 



Internal to the granular layer of ectosarc lies a very much thicker 

 laj^er which shoAvs numerous alveoles ^ of various sizes. It was 

 from the ectosarc of Opal'ma ranarum that Biitschli first got his con- 

 ception of alveolar structure of protoplasm. Within the larger 

 alveoles are bodies of material, of considerable size, often roughly 

 globular in form, which I have previously called ectosarc spherules. 

 In figure 3 these are rather darkly stippled. Their chemical nature 

 is undetermined. Their connection with the nutritive function, while 

 probable, is not demonstrated. Throughout the ectosarc, in the films 

 between the alveoles, are niunerous granules, cytomicrosomes, ap- 

 parently exactly similar to those in the endosarc. No cytomicrosomes 

 are shown in figure 3. 



Internal to the ectosarc lies the endosarc, occupying the axial 

 region of the body. It is alveolated, but usually with alveoles much 

 smaller than those of the ectosarc. Many of the endosarc alveoles 



8 Bezzenberger (1904) described basal granules elongated perpendicularly to the pellicle 

 in Cepedca longa. In my specimens of what seems to be C. longa I find spherical basal 

 granules. 



' 1 am not attempting to use this word in Biitschli's sense. Indeed I am not certain to 

 just what struclures Biitschli would apply this term. 



