494 CHARLES W. HARGITT 
INTRODUCTION 
In the course of investigations carried on by the writer during 
several years, certain facts have come to light which seem to 
have important bearings upon several problems of general 
ontogeny. Invarious papers phases of these have been suggested, 
but only incidentally has any attempt been made to discuss their 
significance or their probable correlations as developmental 
phenomena. With further investigations still additional facts 
have been observed, and similar investigations by others have 
tended to convince me of their importance in a still larger degree. 
When the honor to codperate in the preparation of this memorial 
volume was submitted, it seemed that no more appropriate sub- 
ject came within the scope of the writer’s researches than that 
involved or implied in the above caption. 
My introduction to coelenterate morphology began many years 
ago with the problem of the origin of sex-cells, a subject at that 
time brilliantly exploited by Weismann, whose “‘Entstehung der 
Sexualzellen bei den Hydromedusen, Zugleich ein Beitrag zur 
Kentniss des Baues und der Lebenserscheinungen”’ (’83), has 
long been a recognized classic in its line. It was ably supple- 
mented by the hardly less brilliant researches of Metschnikoff 
(86), ‘“Embryologische Studien an Medusen. Ein Beitrag zur 
Genealogie der primitiv Organe.”’ 
The first contribution to the subject by the writer was a very 
brief and tentative paper before Section F, of the American Asso- 
ciation for the Advancement.of Science, in 1889. It was adversely 
commented upon by one who had accepted without question the 
then prevalent dogma that Hydrozoa were distinguished from 
all other Cnidaria by the origin of the sex-cells exclusively from 
the ectoderm. Under this adverse criticism no further utter- 
ance was made on the subject for several years, though there was 
no lapse of interest or investigation. 
In the meantime, an observer here and there had dared to 
question the conclusiveness of the earlier dogma. Little by lit- 
tle facts were accumulating which cast further doubts upon the 
matter, and even compelled the conclusion that Weismann’s 
