INTERNAL ANATOMY. 81 



THE REPRODUCTIVE ORGANS. PL B and PL C, 

 figs. 1, 11. 



Nalepa* is strongly impressed with the similarity of 

 the reproductive system in the two sexes of the Tyro- 

 glyphidae ; this, however, does not appear quite as 

 great to my mind as it does to that of the eminent 

 Austrian acarologist; I should have thought that in 

 some other families of Acari, e. g. the Oribatidae, the 

 resemblance was stronger. It is quite true, as Nalepa 

 says, that in both sexes the true reproductive, or ger- 

 minal, glands are two paired organs whose ducts do 

 not coalesce until near the external sexual organ ; but 

 the intermediate course of those ducts and their develop- 

 ment is very different in the two sexes. In the female 

 the ring-form, so common in these organs in the Acari, 

 is carried to its fullest extent ; in the male it can 

 scarcely be traced. It is also true, as Nalepa says, 

 that in both cases each of the above-named reproduc- 

 tive glands is at first a nucleus-bearing plasma-mass 

 not distinctly defined into cells ; it is by a slowish pro- 

 cess that a portion of the plasma surrounding each 

 nucleus gradually defines itself as an independent cell 

 containing the nucleus, and becomes a germ-cell or a 

 spermatoblast, as the case may be. The Tyroglyphidae 

 doubtless vary considerably from the higher Acari in 

 the structure of the genitalia and the development of 

 the sexual products ; yet in the higher Acari a similar 

 plasmodic mass containing nuclei is often found, and 

 Bertkau describes it in some spiders, e. g. the Agele- 

 nidae.f When the Imago, of either sex, emerges from 

 the nymphal skin the internal sexual organs are com- 

 paratively small ; although even then they are of sub- 

 stantial size ; but when the sexual products are fully 

 developed and the oviducts are occupied by eggs or 



* 'Abth. I/p. 206. 



f " Ueber den Generationsapparat der Araneiden," in ' Arch. 

 Naturg.,' 41 Jahrg. (1875), p. 244. 



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