102 
REVIEWS. 
Zur kenntniss des generationswechsels und der Parthenogenesis 
bei den Insecten. Von Rup. Levcxart. Mit 1 Tafel. 
(From Moleschott’s ‘ Untersuchungen zur Naturlehre des Menschen und der 
Thiere,’ 1858.) 
Tue author commences with some general remarks on the 
bibliography and history of the subject,* and proceeds to 
describe the ovaries of the oviparous and viviparous Aphides. 
His observations on these insects, though not carried so far, 
agree very closely with those previously made by Professor 
Huxley. 
In the Coccide, Leuckart has examined species belong- 
ing to the genera Coccus, Lecanium, and Aspidiotus. As 
to the general form of the female generative organs in L. 
hesperidum, he confirms the observations of Professor Leydig. 
The type of egg-formation in this species much resembles 
that found in Aphis, and the egg is truly agamic. 
Prof. Leuckart differs in many respects from the observa- 
tions made by Professor Leydig. He states that the germi- 
nal vesicle, though easy to be overlooked, is really present ; 
that the vitellogenous cells take no part in the formation of 
the embryo; and that the ovarian product is a true egg, 
which, however, when laid, contains an almost mature em- 
bryo, which is very soon hatched. In C. adonidum the 
embryo is less developed at the time when the egg is laid. 
Prof. Leuckart concludes with some general remarks on 
agamic reproduction, and proposes to restrict the term ‘ Par- 
thenogenesis’ to those cases where the egg, which is capable of 
spontaneous development, is also susceptible of impregnation. 
It is impossible, without exceeding our limits, to do more 
than glance at the interesting and valuable observations 
contained in this paper, the excellence of which will be fully 
appreciated by those who have made this branch of science 
their peculiar study, and which will fully sustain the repu- 
tation of its author. 
* Tn referring to the Daphniz he uses the term ‘ agamic eggs,” as syno- 
nymous with the so-called “ winter eggs.” Mr. Lubbock, however, has 
shown that while the common sort of egg is in Daphnia certainly agamic, 
the winter- or ephippial-eggs require impregnation. 
