98 POPULAR SCIENCE MONTHLY. 



in the case of the armadillo, Tatusa hyhrida of Paraguay. The eight 

 to eleven young of each birth are always of the same sex. This occurs 

 also, it is said, in another species, Tatusa novemcinta. In the latter 

 case it was found by Jehring that all the embryos of one birth are 

 enveloped in a common chorion, although each has its own separate 

 placenta. It is probable that these embryos are the product of a single 

 egg that has become separated during the early stages of segmentation 

 into as many parts as there are embryos produced. That separated 

 blastomeres or cells are capable of giving rise to whole embryos has 

 been demonstrated experimentally in recent years for a number of 

 animals. 



The following discovery also bears on the same question. A 

 hymenopterous insect, a chalcid bee, Encrytus fiLScicollis, lays one or 

 two eggs in the egg of a caterpillar that is to become the host. The 

 egg of the parasite develops inside the body of the young caterpillar, 

 not into a single embryo, as is the rule, but into a chain of embryos. As 

 many as a hundred embryos may come from the same egg, all united in 

 a common amnion. It has been observed that the bees that emerge 

 from the same caterpillar are frequently of the same sex. Thus in 

 twenty-one observations the progeny was in fourteen cases all of the 

 same sex. In the remaining seven cases both males and females 

 appeared. In the former it is probable that only a single egg had been 

 laid in the egg of the butterfly, and in the latter more than one egg 

 may have been deposited. 



One of the earliest and most important of the recent memoirs that 

 have attempted to show that the sex of the individual is determined in 

 the egg is that of Cuenot.* This paper deserves first place not only 

 because in point of time it precedes the others to be mentioned, but 

 also because the author has undertaken a considerable number of 

 important experiments that bear on the problem of the determination 

 of sex. 



It had been claimed that when young caterpillars are poorly 

 nourished they give rise to a larger number of males, and conversely, 

 when well nourished to a great majority of females. The experiment 

 was first carried out by Landois, and later confirmed by Giard, Treat 

 and Gentry. On the other hand, Eiley found that starved caterpillars, 

 as well as those abundantly supplied with nourishment, give both 

 male and female individuals with no greater disproportion in numbers 

 than ordinarily exists. Other observers have recorded similar results. 

 Furthermore, a number of investigators have shown that the sex of 

 the young insect is already determined at the time when it emerges 

 from the egg and even some time before that event. Brocadello's 



* Bulletin Scientifique de la France et de la Belgique, XXXII., October, 

 1899. 



