THE 
AMERICAN: NATURALIST 
Vor. XXXIV. March, 1900. No. 399. 
ON THE LIFE HISTORY OF AUTOLYTUS COR 
NUTUS AND ALTERNATE GENERATION 
"IN ANNELIDS. 
P. CALVIN MENSCH. 
Tne claim for the presence of an alternation of generation . 
in annelids owes its origin chiefly to the results obtained in 
study of the family of syllidians by the earlier authors, Milne- 
Edwards, Savigny, De Quatrefages, Krohn, and more recently 
by A. Agassiz. What subsequent proofs of the presence of 
this condition in annelids have been presented still find their 
Strongest support in the phenomena observed in a division of 
this family, that of Autolytus. 
In forms of Autolytus, like Autolytus cornutus, described by 
Agassiz, after the young and so-called asexual animal has 
attained a certain length,a new head is developed on the four- 
teenth setigerous segment, and in this way the individual 
becomes divided into what is known as the parent stock, 
including the original head with its segments, and the bud or 
stolon, including the new head with the remaining segments. 
The stolon contains the maturing sexual products, and after 
these reach a certain stage of maturity it separates from the 
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