LIFE HISTORY OF TWO RARE CILIATES 383 



and was in no sense related to the 'chromidia' of Schaudinn, 

 or the idiochromidia of Mesnil. 



I did not find in either Spathidium or xA.ctinobolus any struc- 

 tures which I felt justified in interpreting as micronuclei. The 

 only bodies which in any way resembled these organs in struc- 

 ture were much too large to be so interpreted. In these organ- 

 isms both vegetative and propagative chromatin are combined 

 in the long cord-like nucleus, the form and extent of which vary 

 to a remarkable degree. According to Btitschli, the primitive 

 nucleus of the ciliate cell was doubtless spherical, a condition 

 which is found in almost all small ciliates. Using such a type 

 as a starting point it is interesting to follow the evolution of 

 this organ through the ellipsoidal condition, to the short band 

 or rod-shape, on to a greatly elongated nucleus twisted into 

 a complicated coil or divided into numerous ellipsoidal masses 

 enclosed in a common membrane, the increase in length in most 

 cases being coincident with the elongation of the cell body. 

 In 1903 Richard Hertwig first discussed his theory of the nu- 

 cleus-plasm-relation, maintaining that for each kind of cell in 

 a normal condition, there exists a definite relation between 

 nucleus and protoplasm, upon which the vitality of the cell 

 depends. He called attention to the fact that this normal cor- 

 relation between cell-size and nuclear-size is destroyed by changes 

 in environment, as for example, an increase or decrease in tem- 

 perature, starvation or overfeeding, which affect the metabolic 

 activities of the cell controlling the exchanges of nuclear and 

 cytoplasmic material. As a result of this increase of nuclear 

 material, the cell shows symptoms of senile degeneration which 

 end in death unless the normal cell-relations are restored, either 

 by direct elimination of the nuclear material, or by conjugation. 

 In support of his own results, based upon the study of Actino- 

 sphaerium and Dileptus under different environmental condi- 

 tions, he cited the conclusions reached by Boveri in the case 

 of the sea-urchin larvae and by Gerassimow in his work on 

 Spirogyra. 



In 1902 and 1905 Boveri studied the relation of cells and 

 nuclei in sea-urchin larvae containing X, 2 X, and 4 X numbers 



