290 LECTURES ON BIOLOGY 



then put on its most brilliant nuptial dress, and performs before its 

 mate the queerest contortions. Finally his efforts are rewarded 

 with success, for the sexual desire is aroused in the female. The 

 triton now deposits on the ground, before the eyes of his chosen 

 mate, several spermatophores. The female crawls upon them 

 and takes them up with her sexual organs, in which they open 

 and liberate the spermatozoa, when fertilization takes place. 

 We find a similar process in our native myriapods, the Scolo- 

 pendra. Here the male attaches his spermatophores with self- 

 spun threads to the earth ; then the female receives them in her 

 sexual organs. 



Frogs unite for the purpose of fertilization. The male sits on 

 the back of the female, holding her with his fore-legs and wait- 

 ing until she discharges the ova, when he pours the sperm upon 

 them. Fertilization, therefore, is here external. 



In animals which have no external sex-organs, copulation 

 and transmission of the semen is performed by pressing together 

 the sex-apertures. In such case it happens sometimes, as, for 

 instance, in the earth-worm, that both copulating animals become 

 firmly joined together by elastic bands, secreted by a glandular 

 organ, the clitellum. More frequently it happens that the male 

 sexual passage ends in a protruding or protrusible penis which, 

 during copulation, is introduced in the female vaginal orifice, and 

 thus transmits the male sperm-cells with much greater certainty. 

 Sometimes other parts of the body may be employed for this 

 purpose, when they become suitably transformed. 



In the crayfish, for instance, it is the two most anterior 

 pairs of abdominal feet that serve as instruments of copulation. 



In the male spiders, the palpus has as its point a pear-shaped, 

 sac-like process, furnished with a spiral thread, the ' palpal 

 organ.' Before the spider approaches his mate he fills this 

 sac from the germinal gland with sperm, and thrusts it at 

 the moment of copulation into the vaginal orifice. He must, 

 however, proceed most cautiously, for the female is in many 

 species considerably larger and stronger. With the strangest 

 contortions the male endeavours to approach the female, but only 

 too often it happens that she rushes upon him and kills him. 

 Even if he has successfully braved all dangers and reached the 

 goal of his desire, he must, after completed copulation, quickly 



