386 The Unity of the Organism 



the test of the daughter-cell. When the bud has reached a 

 certain size, the plates or particles which are to form the 

 shell move out through the mouth-opening of the parent 

 shell and forai around the protoplasm of the bud. In the 

 meantime the nucleus (N) undergoes division, and, in the 

 case of Euglypha at least, the daughter-nucleus is the last 

 element to leave the parent organism." ^^ 



Assuming this account to be essentially correct — and 

 there seems no reason to doubt that it is — can any candid 

 person refuse to believe that the protoplasm is at least in 

 part the actual cause of its own extrusion from the mouth- 

 opening of the shell, of the production of the plates (in 

 species in which these are secreted), of transporting them 

 to their final position, and of arranging them into the shell 

 of the new individual? And can any one refuse to admit 

 that the whole formative process is a manifestation of 

 heredity.^ But if one admits these contentions he perforce 

 admits that the cytoplasm is a physical basis of heredity 

 if any substance at all can be properly so considered. 



(/^) The Clinging Organs of Sporozoa 



The Sporozoa being poor in organs of locomotion and of 

 contact with the external world, in comparison with the 

 higher Ciliata, Flagellata and Radiolaria, afford less op- 

 portunity than these latter for studying the participation 

 of different substances of the body in organ production. 

 However, the differentiation of the body into segments in 

 many species, and the appearance of anchoring spines and 

 hooks by which the creatures cling to their hosts, make them 

 favorable for such studies. The developmental stages of 

 Pyxinia mohuszi shown in figures 28 a, b, c, should be re- 

 called, as should also the question whether the probability 

 that the root-like epimerite ep''m which penetrates deep 

 into the host cell, is "determined" largely if not wholly by 



