ABSTRACTS OF PAPERS 



PRESENTED AT THE MEETINGS UK THE 



AMERICAN MORPHOLOGICAL SOCIETY 



AT BALTIMORE, DECEMBER 27 AND 28, igoo. 



I. FISSION AND REGULATION IN STENO- 

 STOMUM LEUCOPS. 



C. M. CHILD. 



THE single individual of Stenostomum differs considerably 

 in size, according to conditions. Well-nourished specimens 

 may reach a length of nearly one and one-half millimeters, 

 while specimens measuring only one-half millimeter are often 

 found when food is scarce. The length is about eight or 

 ten times the transverse diameter. 



The animals usually occur in chains, the number of zooids 

 varying from two to nine. Ordinarily chains do not consist 

 of more than five zooids, the uneven number being due to the 

 fact that the anterior zooid precedes the others in division. 

 The short chains of two or three zooids occur when food is 

 scarce. In well-nourished specimens the fissions succeed each 

 other more rapidly, and longer chains are the result. Each 

 particular septum occurs, with little variation, in a definite, 

 characteristic position, this apparently being determined largely 

 by the relative degree of development of the two ends of the 

 zooid which it divides. 



Entodermal tissue is necessary for regeneration. Portions 

 containing all the other tissues of the body except entoderm 



3 2 9 



