INSECTS. 269 



with in most Insects and which unite with the efferent canal. That 

 these parts rather serve to effect special secretions and correspond 

 with the prostate and COWPER'S glands in higher creatures is pro- 

 bable even from their composite structure ancl great development. 

 Hence in some Insects they have been even described as testiculi 

 and the true testes as glands of an unknown use, as for instance, by 

 SwAMMERDAM in Oryctes nasicornis 1 . In this and other Lamelli- 

 cornia (Melolontha, Cetonia) these glands are two tortuous canals, 

 which resemble the testiculi of the Carabici. In Hydropliilus piceus 

 these parts exceed the testes in circumference. Ordinarily there is 

 one pair 2 : often also there are two pairs of these accessory organs 

 present; in some are found three or even more pairs. They are 



.ntirely absent only in few Insects (G-ersis, Velia, Ranatra). In 

 Libellula they are also wanting 3 ; yet I think it is nearer the 



ruth to say that here they are not connected with the testiculi 



md are present in an unusual situation, which is in agreement with 



he copulation of these animals 4 . From this also it is apparent that 



hese organs are not vesiculce seminales. 



For determining the purpose of the different parts connected 

 tvlth the organs of propagation microscopic investigation in the 



ecent state is of great service. C. TH. VON SIEBOLD has never 

 met w^ith spermatozoa in the parts which we consider subservient to 



pecial secretions, which however they ought to contain if they 

 svere really seminal vesicles as LEON DUFOUR and other writers 



uppose. The spermatozoa of Insects are like hairs, and are often 



bund in the testes united in bundles and surrounded by a transpa- 



ent covering 5 . 



We must notice, in addition, that in many species of Insects a 

 !reat similarity of form has been observed between the organs of 



propagation in the two sexes. We see this resemblance in certain 



1 Bijbcl der natuur. Tab. xxx. fig. 8, m m; these are the true testes. I could almost 

 uppose that LEON DUFOUE so indefatigably laborious in the anatomy of Insects and 

 o rich in experience, has made the same mistake in Ptlogonus ; see the Rech. sur Ics 

 lemipt. PI. xi. fig. 137 A., where I consider the spiral organs b b to be testes. 



2 As in the Hymenoptera, for instance. 



3 LEON DUFOUR, Mem. presentes, vn. p. 572. 



4 See below, in the systematic arrangement, in the family of the Libellulina. 



5 See VON SIEBOLD, Ueb. die Spermatozoen der Crustac.een, Inscctcn, Gasteropoden 

 t. einiger anderen wirbettosm Tkiere, MUELLER'S Archiv. 1836, s. 10 43, Tab. if, . 



