156 The American Naturalist. [February,. 
act of laying, as seen and described by Boreri in S. bipunctata, the 
sausage-form that these eggs pass through being given them in the latter 
case by pressure while still in the ovary. 
Mr. Conant was unable to determine definitely the location where — 
fertilization takes place, but supports Hertwig in affirming contra Grassi: 
that no spermatozoa are found in the ovary. What little evidence he 
has indicates that fertilization takes place while the ova are in the duct. 
between the exterior opening and the opening of the duct of the recept-- 
aculum seminis. Self-fertilization seems impossible. 
The eggs when laid become attached to the sides of the dish by a 
gelatinous substance that facilitates handling, but collects dirt. Im 
warm weather development to hatching takes place in about 36 hours, 
and then the animals are miniatures of the adult form, and all are as- 
ready to devour their comrades as are the mature animals.—F. C.. 
KENYON, 
The Chetognaths of American Waters.—In his paper just. 
cited Mr. Conant gives nine species as the total number known to occur 
in American waters. Among them he enumerates five new species added 
by himself. One of these has caused him to make some very pertinent. 
remarks concer ning the divisions of the old genus of Sagitta into Sagitta,. 
Krohnia, and Spadella. He agrees with Béraneck’s criticism of the 
systems proposed by Langerhans, Hertwig, and Grassi, and like this. 
author concludes, though under protest, to follow with Strodtmann the 
arrangement proposed by Langerhans. It would have been much 
- better, however, had he obeyed the impulse that his new species pro- 
duced, and described all nine as species of Sagitta, instead of sand- 
wiching species of Krohnia and Spadella in irrregularly between un- 
doubted species of Sagitta. Or he might at least have placed the terms 
Krohnia and Spadella in parenthesis. 
But, notwithstanding the doubt that arises as to which of the older 
arrangements to follow in placing Mr. Conant’s new species, it should 
be remembered that after all any system of classification is very largely 
for convenience, and that in the present state of our knowledge, not only 
of this particular group of animals but of the fundamental laws gov; 
erning the evolution of one form from another, any system proposing 
to show genetic relationship is at least only tentative, and often weakly 
so at that. In this particular case whether we should regard the number 
of fins with Hertwig, the so-called teeth, or with Strodtmann and Béra- 
neck, the sum of the characters as the determining features is still a 
doubtful matter. Judged from the standpoint of convenience the ar- 
