116 BKITISH APHIDES. 



genesis, and Leuckart proposed the term Arrenotohy 

 to express the power of certain virgin females to 

 produce males.* 



2. THE REPRODUCTIVE ORGANS OF THE VIVIPAROUS 



APHIS. 



The body-cavity of the viviparous Aphis during the 

 summer time is almost exclusively occupied by the 

 embryos and the organs subservient to nourishment. 

 In Aphis proper, in Siphonophora, and the higher 

 genera, the embryos are exceedingly numerous. As 

 many as thirty may be often counted, if the abdomen 

 be snipped with sharp scissors, and the insect be com- 

 pressed under the microscope. These embryos may 

 be seen in all stages of maturity ; those placed nearest 

 the vulva being by far the largest, and showing the 

 eyes, antennas, and limbs fully formed. Their posterior 

 ends are turned towards the vulval opening. Thus 

 the young ones are always born tail foremost. 



The first thing which calls attention is the multi- 

 plicity of the ovarian chambers. As in most insects, 

 these coeca unite end to end, and form several long 

 strings, somewhat like threaded beads of different sizes. 

 These strings ; which vary in number in different 

 species, compose two bundles or fasciculi, one of each 

 is disposed laterally. Each fasciculus unites with an 

 oviduct ; and finally the two oviducts coalesce before 

 11 icy join the vaginal passage. 



Thus the ovarian chambers are largest at their 

 attachment to the ovarian duct, and become more and 

 more attenuated as they penetrate deeper into the 

 body-cavity. The terminal chambers are very small ; 

 but each has a delicate filament united to the anterior 

 part, supposed by some to be in communication with 

 the organ which lias the function of a heart. 



This end chamber is the seat of important action, 

 for within it the first germinal matter is elaborated. 



* Dv. Burnett's transl. Von Siebold's ' Comp. Anat.' 



