No.411.] REVIEWS OF RECENT LITERATURE. 233 
frequently in late embryonic stages. It may be that here, and in 
other insects whose eggs have a thin chorion, there is need that the 
egg be coated with saliva to prevent its drying up. Whatever the 
influence of the secretions of the three pairs of salivary glands, sex 
in bees is determined by the existence or absence of fertilization. 
Other conditions within the sex — whether, for example, worker or 
queen shall result — may be determined (as they apparently also are 
in termites, according to Grassi's observations) by the quantity and 
quality of the food, including the salivary secretions. How it is that 
fertilization determines sex is not known, but that it does can no 
longer be denied. 
Dickel has insisted that there is a difference between drones pro- 
duced by fertile workers and those produced by queens, and he 
believes that the former are infertile. Weismann says he knows of 
no proof of this, but admits that the studies of Petrunkewitsch show 
that there is a slight, though constant, difference in the early phe- 
nomena of development between unfertilized eggs from queens and 
those from workers, and that this may possibly be of importance. 
Further study on this point is required. A difference between queen- 
drones and worker-drones is a priori in no way improbable; indeed, 
there is a wasp in which two kinds of drones are known to exist, 
though it is not known whether these have the same or a different 
parentage. m. 
Artificial Parthenogenesis. — Following the lead of Morgan and 
Loeb, who have shown that certain salts can induce the development 
more or less complete of unfertilized eggs of the sea-urchin, Pieri * 
and Winkler? have, independently of each other, tried to induce 
development of the unfertilized echinoderm egg by means of sperm 
extract. Their efforts have been at least partially successful, though 
the observations made are less extensive than might be desired. 
Pieri took fresh, sound sperm of Strongylocentrotus lividus, or of 
Echinus esculentus, and shook up the same either in sea water or in 
distilled water. The fluid was then filtered and examined under the 
microscope. It was found to contain still a certain number of sperma- 
tozoa, but these were motionless, rounded, tailless, and, so far as 
direct observation could show, dead. Unfertilized eggs of the species 
from which the sperm was obtained were then placed in some of this 
! Pieri, J. B. (99), Exp. (3), 7, Notes et revues, Arch. de Zool., p. xxix. = 
2 Winkler, H. (1900). Nachrichten v. d. k. Gesellsch. d. Wiss. Gottingen, 
Math -phys. Klasse, p. 187. 
