THE SPERM A TOZOA 



497 



The ejaculatory duct during coition conducts the sperm 

 into the copulatory pouch of the female. In conse- 

 quence of the stretching of the integumental membrane 

 the end of the duct can be erected and again withdrawn. 

 For this purpose the end of the duct is thickened and 

 is said to be provided with powerful muscles. The 

 evaginable terminal portion is covered by a strong chiti- 

 nous membrane forming the penis or intromittent organ 

 (Fig! 462, 7i), which is externally enveloped by a pair of 

 chitinous lobes, which in many beetles are converted into 

 a capsule. The ductus ejaculatorius of the honey-bee is 

 inserted by two chitinous branches into the point of 

 union of the two glandulae mucosse; it and the entire 

 copulatory apparatus are devoid of muscles, though it is, 

 however, well developed beneath the mucous glands. 

 (Koschewnikoff.) 



The accessory glands of the vasa deferentia are tubes 

 whose secretions either directly mix with the semen, 

 or in many cases form seminal packets (spermatopJiores). 

 In Coleoptera, Lepidoptera, and Diptera there is usually 

 one pair. In many insects there are several pairs, as in 

 Hydrophilidce and Elateridae; they are branched in 

 Hemiptera, and in Orthoptera bushy. The single 

 glandular tubules are very long, and form a skein- J^ 

 like mass. In Orthoptera, in the larger number 

 of accessory glands, two forms may be distin- 

 guished, which differ from each other in their 

 contents (Siebold). In the cockroach (Fig. 461) 

 these glands form the " mushroom " shaped gland 

 of Huxley, which was at first regarded as the 

 testis. 



The spermatozoa. - - These very minute bodies, 

 the sexual homologues of the eggs, abound in the 

 seminal fluid, and are formed in the follicles of the 

 testes from a germinal layer or epithelium, as are 

 the eggs. They are hair- or thread-like, usually ^ 

 consisting of a head, a body or middle-piece, and SffJ 

 a long, thread-like tail (flagellum), which vibrates 

 rapidly, causing the spermatozoon to move actively ?" ( ' a fi 



J *(/); i>, 



forwards (Fig. 470). 



a. 



n 



/ 



In beetles, according to Ballowitz, there are two main 

 types of spermatozoa, connected, however, by intermediate 



2K 



e envelope 

 nucleus ; , a, 

 apical body divided into 

 two parts. S, anterior 

 part of that of Calathus, 

 with barbed head and fin- 

 membrane. After Bal-- 

 lowitz, from Wilson. 



