r 



-t 



' 



lives. Griiber found that an ActinopJirys when transferred from fresh 

 into sea water soon loses its vacuoles ; and, vice versa, when trans- 

 ferred back to fresh water, again acquires its vesicular appearance. 

 In general appearance a radiolarian resembles a heliozoon, but there 

 is a considerable difference in the corresponding regions. A typical 

 radiolarian can be conceived if we imagine a thick perforated chitinous 

 membrane between the ectoplasm 

 and endoplasm of a heliozoon. The 

 intra-capsular plasm (Fig. 33, c) 

 contains nuclei, fat particles, and 

 plastids of one form or another, 

 and is in communication with the 

 extra-capsnlar plasm through the 

 pores in the membrane, although, 

 as shown by Verworn's experiments 

 upon the isolated central capsule, 

 it can live for a time independently. 

 The outer or extra-capsular plasm 

 is composed, according to Haeckel, 

 of four parts. The outermost {g) 

 is a zone of pseudopodia ; the latter, 

 however, originate in the deeper 

 fourth zone, forming a network 

 through the other extra-capsular 

 parts. The second zone is of net- 

 like (alveolar ?) protoplasm, the 

 sarcodictyum. A third zone, the 

 calymma, is of jelly-like consistency 

 and forms the bulk of the ecto- 

 plasm. The fourth and most im- 

 portant zone, the sarcomatrix, lies 

 close against the central capsule, 

 and is the go-between for the intra- 

 and extra-capsular portions. The 

 sarcomatrix is also the seat of di- 

 gestion and assimilation, the food 

 coming to it through the pseudo- 

 podia and the network. As the 

 means of communication between 

 the central protoplasm and the sar- 

 comatrix is of vital importance to the organism, the arrangement of the 

 apertures in the central capsule offers a good character for the classifi- 

 cation of the Radiolaria. Hertwig ('79), who first used this character, 

 divided the group into four legions, as follows: (i) the Peripylea, in 



Fig. 33. The protoplasmic regions of a 

 radiolarian ( Thalassicolla maculata) Haeck. 

 [HAECKEL.] 



a, large alveoli forming part of the calymma 

 in which foreign bodies (b) are enclosed, and 

 which is penetrated by meshes constituting the 

 sacrodictyum ; c, the central capsule and intra- 

 capsular plasm ; f, retracted pseudopodia. The 

 nucleus (n) contains a distinct nucleolus (/); 

 the sarcomatrix is darkened by pigment 

 masses (p). 



