31^ 



PERIPATUS, MYRIOPODS, AND INSECTS. 



Reproductive Organs. 



Male. 



Female. 



The paired testes usually consist of 

 many small tubes. 



Two ducts (vasa deferentia), con- 

 ducting spermatozoa (perhaps in 

 part comparable to nephridia). 



An unpaired terminal and ejaculatory 

 duct, paired and with two aper- 

 tures in Ephemerids only ; some- 

 times formed by a union of the 

 vasa deferentia, sometimes by an 

 external invagination meeting 

 the vasa deferentia. 



From the vasa deferentia or from the 

 ejaculatory duct, a paired or un- 

 paired seminal vesicle for storing 

 spermatozoa. 



Various accessory glands, whose 

 secretion sometimes unites the 

 spermatozoa into packets or 

 spermatophores. 



Sometimes a copulatory penis. 



Often external hard pieces. 



The paired ovaries usually consist of 



many small tubes (ovarioles). 



Two ducts (oviducts), conducting the 

 ova (perhaps in part comparable 

 to nephridia). 



An unpaired terminal region or 

 vagina, paired and with two 

 aperturesin Ephemerids; usually 

 formed from an external invag- 

 ination meeting the united ends 

 of the oviducts. 



Near or from the vagina, a re- 

 ceptaculum seminis for storing 

 spermatozoa received from a 

 male during copulation. 



Various accessory glands, e.g., those 

 which secrete the material sur- 

 rounding the eggs. 



Sometimes a special bursa copulatrix 



in the vagina. 

 Often external hard pieces, e.g., ovi- 

 positor. 



Some Peculiarities in Reproduction. 



Many Insects, such as aphides, silk moth, and queen bee, are exceed- 

 ingly prolific. The queen termite lays thousands of eggs "at the rate 

 of about sixty per minute " ! 



The store of spermatozoa received by the female, and kept within the 

 receptaculum seminis, often lasts for a long time, — for two or three years 

 in some queen bees. Sir John Lubbock gives the remarkable instance 

 of an aged queen ant, which laid fertile eggs thirteen years after the last 

 union with a male. 



Parthenogenesis, or the development of ova which are unfertilised, 

 occurs normally, for a variable number of generations, in two Lepidop- 

 tera and one beetle, in some coccus insects and aphides, and in certain 

 saw flies and gall wasps. It occurs casually in the silk moth and several 

 other Lepidoptera, seasonally in aphides, in larval life in some midges 

 {Miastor, Chironomus)^ and partially or "voluntarily" when the queen 

 bee lays eggs which become drones. Parthenogenetic ova (in water 

 fleas, Rotifers, &c.), are believed to form only one polar body; the egg 

 which becomes a drone forms two as usual, but the case of the bee is in 

 several respects exceptional. 



A few insects hatch their young within the body, or are "viviparous." 

 This is the case with parthenogenetic summer aphides, a few flies, the 

 little bee parasites Strepsiptera, and a few beetles. 



