EXPLANATION OF SYMBOLS AND LETTERS. 139 



The anatomy of the spermatheca and the muscular apparatus of its 

 duct for delivering the spermatozoa to the egg does not, as Breslau 

 points out, throw any light on the determination of sex in bees. It is a 

 common notion that all eggs of an unfertilized female develop into 

 drones, but this is by no means proved; in fact, there is just as good 

 reason for believing that, while no females develop, there are also no 

 more than the normal number of drones produced — the eggs that 

 might otherwise have developed into females, if laid by a fertile queen, 

 all dying in the cells of the comb, from which they are removed by the 

 workers. Modern investigation of the determination of sex shows that 

 there is probably just as much reason in many cases for supposing that 

 sex is established in the egg of the ovary before fertilization, as there 

 is for believing it to result from fertilization or from subsequent en- 

 vironment of the egg or young embryo. Hence, it is not only very, 

 doubtful that the queen determines the sex of her offspring by con- 

 trolling the fertilization of the eggs, but it is also very uncertain that 

 fertilization itself has anything to do with it. Parthenogenesis in 

 the bee may amount simply to this, that the male eggs, predetermined 

 as such in the ovary, are capable of developing without fertilization, 

 while the female eggs are incapable of such a development and die if 

 they are not fertilized. 



Each unlaid egg of insects in general has a small hole in the upper 

 end of its shell, called the micropyle, which admits the spermatozoa to 

 its interior. One or several spermatozoa may enter the egg through 

 this aperture, but the nuclear part of only one unites with the egg 

 nucleus, this constituting the fertilization of the egg. After this the 

 micropyle closes and the egg is deposited in a cell of the comb by the 

 queen. The nucleus and a part of the protoplasm of the egg then 

 begin to split up into a number of small cells which — but this is 

 taking us into the development of the next generation, which is 

 beyond the limits of our subject, and so here we must stop. 



EXPLANATION, OF THE SYMBOLS AND LETTERS USED ON THE 



ILLUSTRATIONS. 



The writer has made an attempt to work out a set of convenient 

 symbols for all the principal external and internal parts in the anat- 

 omy of an insect. It has been found, however, that entire consistency 

 is incompatible with practicability, especially in making compound 

 abbreviations, and, therefore, the latter has been given first considera- 

 tion in many cases. For example, the symbol Dct suggests the word 

 " duct " when standing alone much better than simply the letter Z>, 

 but such combinations as SalDct and OvDct are unnecessarily long 

 and the shortened forms of SalD and OvD are sufficiently suggestive 

 of " salivary duct " and " oviduct." The abbreviation So is used 

 in such compound symbols as PsnSc for " poison sac " and TraSc 



