722 



THE GENERATIVE ORGANS. 



As has already been pointed out, there are apparently closer 

 affinities between the Pnsecta and the solid-bodied Worms, 

 than between the Insecta and the Annelida, which are more 

 frequently compared with them. 



The Turbellaria have the same spongy reticulum between 

 their internal organs ; as has been already stated, both the 



f 



Ki<:. 103. Diagram of the generative organs of a Klialuloc'clian (after (JrafT).* 

 /' c, hursa copulatrix ; g, germogen ; r s, receptaculum seminis $ ; /, /, testicles ; 

 //, uterus ; 7 1 , v, vitellogen ; v s, vesiculus seminalis $ ; , common genital duct. 



remarkable metamorphoses of Insects and some peculiarities 

 of their embryo arc foreshadowed in the Nemertid Worms ; 

 and, lastly, the water vascular system of the solid-bodied 

 Worms is probably the homologue of the tracheal system of 

 the Insect (p. 358). 



Two phenomena are observed in the reproductive process in 

 many Trematodes and in some Insects; these are asexual or 



* Planarians, Zool. article ' Encyclopaedia liritannica,' Lond., 



