HARDWICKE'S SCIENCE-GOSSIP. 



33 



all cases the head of the embryo lay south. The 

 question now arises : does the south end of the egg 

 correspond with its lower pole or first laid end? 

 This question must be answered affirmatively, unless 

 we are prepared to admit either, on the one hand 

 that the eggs in laying could have been partly slid 

 under ones already laid, which their thinness and 

 delicacy and their firm adhesion to the glass and to 

 one another seems to render impossible ; or, on the 

 other hand, that the ovipositor of the moth, whilst 



lower pole, we arrive at the conclusion (somewhat 

 important, inasmuch as it is at variance with the 

 statement of Leuckart that "the upper pole in all 

 cases contains the head end of the embryo." — See 

 Entom. Month. Mag. vol. xx. p. 146), that in these 

 eggs the head of the embryo normally occupies the 

 lower pole of the egg. The physiological reason is 

 obvious. In those cases where (as in Pieris brassica:) the 

 egg is attached by its lower pole to the food-plant, 

 the escaping larva, if its head occupied that end, 



NW. 



SW 



NE 



SE 



Fig- 30. 



Fig. 35- 



S.W 



ISte&kS 





Fig. 34- 



Fig. 33- 



Fig. 36. 



4P s.w 



Fig. 





37- 



Fig. 38. 



Fig, 39- 



depositing the egg is bent in under her venter so as 

 to extrude the egg with its lower pole to the front. 

 Such an inversion of the normal orientation does take' 

 place in the case of the sawfly (Zartza fasciata), and 

 probably also, more or less, in the case of other 

 insects laying their eggs in mines or in the ground, or 

 in other situations where a long ovipositor is required, 

 but I am ignorant that there are any grounds for such 

 an assumption in the case of Botys. Taking it for 

 granted then that the south end of the egg is its 



would not only have to eat its way out of the shell, 

 but also through the substance to which the egg was 

 attached ; while in the case of Botys if the head of 

 the larva occupied the upper pole, it would, after 

 eating its way through its own shell, come in contact 

 with the egg above it with disadvantage to itself and 

 probable destruction to its neighbour. 



When I received the eggs on the 4th of August, 

 they were already in the third day of incubation, and 

 presented the following appearances. The yolk- 



