No. 399.] HISTORY OF AUTOLYTUS CORNUTUS. 167 
viduals which have been separated from the parent stock by a 
process similar to that of fission. The parent stock he regarded 
as distinctly asexual and as reproducing only by the separation 
and budding out of sexual stolons. A diagram of Agassiz's 
description of the cycle of generation would therefore be as 
follows : 
Stolon = X < Eggs 
Egg = Parent Stock 
Stolon = X < Eggs 
In this wise he attributed to Autolytus cornutus a distinct 
alternation of generation — in reality the only accurate alter- 
nate generation ever described for any annelid, and his original 
diagram of Autolytus cornutus still stands in some of our recent 
zoólogical text-books as a classical figure for the verification of 
alternation of generation in annelids. 
The asexual condition of the parent stock is, however, not 
as constant as was supposed by Agassiz. In many of the 
specimens examined, particularly in individuals from which a 
first stolon has been separated, sexual products appear in the 
twelfth and thirteenth and even at times in the eleventh seg- 
ment of the parent stock. At the time when the first stolon, 
i.e., the stolon which originally formed a part of the body of the 
parent stock, becomes filled with sexual products none of the seg- 
ments of the parent stock give any indication of the presence of 
reproductive products. In older individuals, however; in which 
apparently after a second or possibly a third stolon has been 
separated, I have found reproductive products in some stage of 
development in a large number of the specimens examined. 
Of such parent stocks found with reproductive products, by far 
the greater number were females, and of these I have been 
able to obtain individuals in which the ova had attained a size 
almost equal to that of mature ova. The different stages in 
the development of the sexual products I have been able to 
follow more successfully in a near relative of Autolytus, Procerea 
ornata, the budding of which is in all respects similar to that 
of Autolytus cornutus. Of this species I have been able to find 
female specimens of parent stocks with ova in all stages of 
development up to the time when the ova are discharged from 
