200 GENERATION AND DEVELOPMENT. 



sJcoleJces right up to the pupa stage ; * on the other hand, 

 the skolekes of butterflies and moths are said to become 

 hampai, or caterpillars, before they become pupae, t The 

 apparently great difference between the caterpillars of 

 butterflies and moths, and the maggots of bees, wasps, and 

 flies, was probably the cause of this difference of treatment, 

 but he considered both caterpillars and maggots to be 

 skoleJces, finally passing into the " real eggs," or pupae. 



His views on this subject are set forth in fairly clear 

 language. He states that Entoma bring forth skolekes at 

 first, but these become egg-like in the course of their 

 development, for the so-called chrysalis is functionally 

 equivalent to an egg. I He also says: "For we must 

 consider caterpillars to be a kind of skolex, and also the 

 [generative products] of spiders, and yet it may seem that 

 some of these and many others resemble eggs, because of 

 their roundness, but they should not be defined by their 

 form, nor their hardness and softness, but by their producing 

 an animal as the result of a change of the whole and not a 

 part. When they have completely attained the skolex form, 

 and have become of full size, they are, as it were, eggs, for 

 the skin hardens about them, and they become motionless 

 at this time. This is evident in the skolekes of bees and 

 wasps and in caterpillars. The reason for it is that, because 

 of the imperfect nature of the animals, their 'eggs' are pro- 

 duced, as it were, before their time, the skolex being, as it 

 were, an egg which is still soft and in process of growth." § 



This is the most important passage on the skolex in all 

 Aristotle's works. It shows clearly, in conjunction with 

 the other passages cited, that his skolex is an immature 

 product of generation, which grows and finally becomes a 

 pupa, or, so Aristotle believed, an " egg," giving birth to the 

 perfect animal. It differed from the egg of a bird, which 

 has a hard shell and does not grow, the young bird being 

 formed from a part only of the egg, the remainder serving 

 as food.jl 



His discussion of the generation of bees is particularly 

 interesting. He refers to the many different opinions which 

 had been given on the subject, and says that much uncer- 

 tainty existed about the mode of generation of bees. He 



* H. A. V. c. 17, s. 5, V. c. 20, s. 1. f Ibid. v. c. 17, ss. 4 and 6. 

 I G. A. ii. c. 1, 7336. § Ibid. in. c. 9, 7586. 



II H. A. i. c. 4, s! 1. 



