No. 399.] HISTORY OF AUTOLYTUS CORNUTUS. 169 
products. Such conditions would strongly indicate that the pres- 
ence of reproductive products toward the close of the phenome- 
non of budding is a constant stage in the life history of these syllids. 
The life history of Autolytus cornutus would, therefore, con- 
sist in: (1) The development, from the egg, of the parent 
stock; (2) the development of sexual products in segments 
posterior to the thirteenth setigerous segment, the development 
of a head on the fourteenth, and the separation of these seg- 
ments for the formation of the free-swimming stolons, Polybos-. 
tricus (å) and Sacconereis (9); (3) regeneration of the lost 
segments and the formation in this way of a second and possi- 
bly a third or fourth stolon; (4) finally, the development in 
the parent stock of sexual products and the conversion of it 
into a sexual individual (Fig. 5). While the sexual products 
are forming, the regeneration of lost segments is still taking 
place, but in none of the specimens found had this new growth 
gone farther than the formation of a small bud, consisting of no 
more than eight or ten distinct segments. 
As compared with a diagram of the cycle of. generation as 
described by Agassiz, we would then have : 
Stolon — x « Eggs 
Eggs — Parent Stock — x « Eggs 
Stolon = x < Eggs 
This would therefore be, not a sexual generation alternat- 
ing with an asexual, but at most no more than a sexual dimor- 
phism — a sexual individual budding off sexual stolons, and as 
its own sexual products mature, partaking more or less of the 
epitokal form of other syllids and itself becoming sexual. 
Alternate generation has also been claimed for chain-form- 
ing syllidians, as Myrianide ; but the presence of reproductive 
products in the posterior segments of the parent stock is of so 
common occurrence that the existence of such a generation has 
already prior to this been disputed by St. Joseph and Malaquin. 
Korschelt and Heider in their text-book of Comparative Em- 
bryology, in accordance with the papers of Krohn and Agassiz, 
describe this process as a true alternation of generation, and 
hold it as distinctly different from the fission in Ctenodrillus, 
