406 HETEROOERA RADICICOLA. 



The excretoi'p system is best observed from the side. It con- 

 sists of a single excretory vessel coming from the intestinal region 

 and opening by a pore some AOfx behind the oesophageal bulb. 



The nervous system is difficult to distinguish, the only indi- 

 cations of its presence being a few fibres, presumably representing 

 the nerve commissure, a short distance behind the oesophageal 

 bulb and just anterior to the excretory pore. 



The full period of development of the male from the egg 

 was found to be nearly four weeks, and the duration of adult 

 life seems to be a little more than three weeks. In ordinary 

 nniall galls, such as aie found on the loots of fruit trees and 

 shrubs, adult males are rarely to be found at the same time as 

 the swollen gravid females. They probablv perish soon after 

 fertilising the young mature female. 



Development of the Female. 



The development of the female parasite closely resembles that 

 of the male up to a certain stage, after which the metamorphosis 

 becomes so peculiar that the final product of the striking changes 

 that occur can scarcely be recognised as a nematode. The evolu- 

 tion of the females involves a retrogressive metamorphosis that 

 is probably a direct result of the parasitic life adopted by the 

 organism . 



The larva destined to develop into a female undergoes the 

 same process of general thickening that marks the early develop- 

 ment of the male from which it cannot be distinguished until 

 a relatively late stage. 



Having assumed the form represented in Fig. 14, the contents 

 of the body are seen to slowly shrink away from the larval skin 

 and eventually a new cuticle is formed under the old one. Gonads, 

 indications of which were occasionally visible as two small groups 

 of cells with distinct nuclei, now commenced to become more 

 prominent. They ultimately come to consist of two ovaries 

 situated at the ends of two caecal tubes, the uteri, which con- 

 verge and unite to form a short vagina, that opens to the exterior 

 by a vulva in close proximity to the anus. While the gonads are 

 developing, the separation of the new organism, replete with 

 spear, alimentary canal, etc., inside the former larval skin is com- 

 pleted. The appearance of the mature female, as the animal 

 now virtually is, still in its larval cuticle, is shown in Fig. 1 r > 

 on Plate VII. The female now undergoes an ecdysis. The spear 

 is employed to pierce the skin and the ecdysis that follows 

 corresponds to the final one undergone by the male. 



In both sexes the individual discards the old larval cuticle 

 that is distinguished bv having the posterior spine-like tail. Only 

 two moults in the evolution of both male and female have thus 

 far been observed, and I am unable to confirm the statement of 

 Stone and Smith (1898) to the effect that four or five ecdvses 

 occur. 



The further development of the female consists of a gradual 

 distension of the intestine in the posterior regions of the body 



