220 ANATOMY- 



margins of the dorsal plate are bent backwards ; it is therefore entirely 

 covered in dry specimens by these margins. Males may be detected in 

 dry specimens by their above thick and clavate abdomen and the larger 

 anal fangs. 



III. DEVELOPMENT OF THE SEXUAL ORGANS DURING THE 



METAMORPHOSIS. 



. 153. 



It is evident, from Herold's * admirable investigation, that even in 

 the larva the germ of the future sexual organ exists, and indeed with 

 the distinctions of male and female. The larvae are born with these 

 extremely small and almost invisible germs, which develope themselves 

 in the course of its life, but most rapidly in its pupa state, until they 

 attain their perfect development upon the full growth of the insect. 



If a caterpillar be opened from the back we observe, after the removal 

 of the fatty substance, upon the intestinal canal, at the posterior ex- 

 tremity of the large stomach, two small roundish or ovate bodies, from 

 which posteriorly two filaments originate, which unite into one canal 

 close to the anus, beneath the rectum. But these filaments are so fine, 

 or become so in their progress, that they almost entirely disappear, and 

 could not be followed to their termination by even the exact Lyonnet. If 

 several larvae, of different sizes and of different ages, be opened, we 

 soon detect differences in these bodies, for some (in Pontia brassicce) 

 are more cylindrical, and are divided by constrictions into four suc- 

 cessive vesicles ; the others are flatter, subsequently ovate,, and by con- 

 strictions from the apex to the base divided into four equal lobes. In 

 the first instance they were small testes, and in the last the preformed 

 egg-bags or ovaries. This form remains unchanged until the pupa 

 state, merely increasing considerably in size. 



In the pupa state the convoluted sperm ducts, and in the female the 

 gluten glands and ovaries, gradually develope themselves. In Pontia 

 Brassica, upon which insect Herold made his observations, the testes 

 gradually approach each other until they lie contiguously. From this 

 common situation a closer connection is formed, the sides press each 

 other flat, and by degrees intimately join together. Thus, from the 

 earlier separate four-chambered testes a simple globose testis is formed, 



' Entwickelungsgeschichtc dcr Schmetterlinge. Kapcl and Marburg, 1815, 4to. uith 

 plates. 



