40 



The reproductive organs. — Although there appears to 

 be no external characteristic by which the sexes of the larva 

 of Corydalis can be distinguished, the internal reproductive 

 organs differ greatly in appearance ; the testes in this species 

 are long and narrow, while the ovaries are short and broad. 

 These organs are situated one on each side, between the 

 layer of adipose tissue which surrounds the alimentary canal 

 and the layer of the same tissue which is attached to the 

 sides of the wall of the abdomen. The testes extend from 

 near the middle of the third abdominal segment to near the 

 posterior border of the sixth abdominal segment. The ova- 

 ries extend from near the middle of the fourth abdominal 

 segment to near the middle of the fifth abdominal segment. 



Determine the sex of the specimen that you are studying. 



Reproductive Organs of the Male. — Note the shape of a testis, the con- 

 nection of it with the respiratory system, the groove in the middle of its. 

 mesal aspect, and the vessel in the bottom of this groove. This vessel is the 

 seminal duct or vas deferens (plural, vasa deferentid) and is the outlet of 

 the testis ; it extends caudad to near the caudal end of the body. The 

 cephalic end of the testis is supported by the ligament of the viscera already 

 described. 



Make drawings showing the external form of a testis. 



Trace out the course of the vas deferens. This will require very careful 

 dissection, especially in the ninth abdominal segment, where the vas defer- 

 ens passes under a muscle. 



The triangular organ into which the two vasa deferentia empty is the- 

 seminal vesicle. If the specimen has been opened on the ventral side, the 

 seminal vesicle will lie on the alimentary canal, but if it has been opened on 

 the dorsal side it will be necessary to cut the intestine and turn back the 

 caudal part of it in order to see the seminal vesicle. 



The tube extending from the seminal vesicle to the external opening of 

 the reproductive organs is the ejacidatory duct. 



Make a drawing showing the relations of the testes, vasa deferentia, semi- 

 nal vesicle, and ejaculatory duct. 



Each testis is composed of many, short, pear-shaped tubes, the testicular 

 follicles, m which the spermatozoa are developed. These tubes open into 



