1918] Yocum: The Neuromotor Apparatus of Euplotes Patella 371 



ization of the nucleus is characterized by the coalescence of its several 

 parts into one body which divides amitotically. Anigstein (1913) 

 finds a nuclear change in Strombidium testaceuni quite comparable to 

 that in Euplotes. In each arm of the macronucleus a diagonal un- 

 colored area appeared. This begins at the middle and works out 

 toward the end, leaving the granules in the central part much larger 

 than those in the undisturbed portion. The author was unable tcr 

 make any suggestion as to the reason for such changes. As will be 

 discussed later in connection with the formation of the cirri, the whole 

 body seems to undergo a reorganization which apparently is of two 

 phases: (1) a period of dedifferentiation characterized by the contrac- 

 tion of the macronucleus and absorption of the old cirri; and (2) a 

 period of formation of the new macronucleus from one-half of the 

 original macronucleus and the growth of new organs. In the introduc- 

 tory paragraph of his well known paper, Wallengren (1901) expresses 

 this idea concisely, "Bei diesen Infusorien (Hypotricha) ist somit auch 

 eine mehr oder w^eniger durchgreifende Renovirung cler Korper beider 

 Sprosslinge mit dem Theilungsvorgang verbunden." Calkins (1911) 

 in a study of the regeneration of Uronychia, operated on before, dur- 

 ing, and after division, found that the power of regeneration was 

 greatest in the early phases of division. He explains this power "on 

 the supposition that substances are formed in the nucleus and trans- 

 ferred to the cytoplasm, where they or the products of their activity 

 accumulate until a condition analogous to saturation is reached." 

 After division is completed and the new organelles are formed, these 

 substances are used up and consequently the power of regeneration 

 is lessened or lost altogether. 



In the light of recent investigations the results of which have been 

 brought together by Child (1915) in his book entitled Senescence and 

 Bejuvenescence, we perhaps are able to put a somewhat different 

 interpretation on such phenomena as take place in ciliates at the time 

 of division. Child has shown that in a study of Paramoecium and 

 Stentor that the earliest indications of binary fission appear not in the 

 nucleus but in the cytoplasm and that these are followed by the 

 nuclear changes. Such changes are characterized by the formation of 

 new cytostomes and contractile vacuoles. He has also proved with 

 dividing infusorians as well as with some of the flatworms, that at the 

 time of division the protoplasm loses its high degree of differentiation 

 and assumes a dedifferentiated or relatively simple condition. Simi- 

 larly with insects at the time of metamorphosis, some of the larval 



