88 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
gated by Salensky (’72), is one of the Loricata. Only Eosphora, upon 
which the work of Tessin (86) was done, belongs, together with 
Asplanchna, to the swimming Illoricata. But even these two are widely 
separated, Eosphora possessing a foot and anus, like the majority of the 
Rotifera, whereas Asplanchna possesses neither. 
The only work which has been done upon the early development of 
any species of Asplanchna is that by Leydig (54) and Lameere (90). 
The latter observed in the living egg of Asplancha Sieboldii the formation 
of the polar cell and the first and second cleavages, but did not carry his 
work further. Leydig (54) observed the cleavage of the egg, and 
figured the four-cell stage in the same species, but does not give any 
detailed deseription. I know of no other work dealing with the early 
development of any species of Asplanchna. 
I have examined the early stages of both Asplanchna Herrickii de 
Guerne and Asplanchna priodonta Gosse, of which the material collected 
in the Great Lakes contained about equal numbers. Asplanchna Herrickii 
was chosen for special investigation on account of the greater size of the 
embryos and adults. The development of Asplanchna priodonta was 
examined for comparison, and notes upon the embryology of this species 
have been given in connection with the fuller discussion of Asplanchna 
Herrickii. 
1. Previous Knowledge of Asplanchna Herrickii. 
It will be well to give here a brief review of previous references in the 
literature to the little known species Asplanchna Herrickii. It was 
first figured by Herrick (84, Plate V.), and described in the explanation 
of plates as “ flask-shaped Rotifer, hermaphrodite, with eges and sperm," 
but no further deseription was given and no name was proposed. 
Herrick in a second paper (°85, p. 61) again mentions this form, but 
adds nothing to the description. 
In 1888, Jules de Guerne ('88) reproduced Herrick’s figure of the 
jaws, and on the basis of this held that the species was new, and pro- 
posed for it the name Asplanchna Herrickii. 
Hudson and Gosse ('89) included Asplanchna Herrickii in their list 
of * doubtful species." 
Daday (792) admits Asplanchna Herrickii as a valid species. 
Up to this time no observer since Herrick had reported finding this 
species. But in this same year, 1892, Wierzejski (92) gave an account 
of its presence in Galicia, with a description, and figures of the jaws 
and the peculiar glandular organ which Herrick had mistaken for 
