Observations on the Orihatidae. By A. D. Michael. 11 



finding any demarcation on the inner side, where they join, nor in 

 removing one from the other without tearing hoth to pieces. The 

 substance of hoth is white, soft, and glandular, but the rounded 

 lobes stain more deeply with logwood, and then exhibit a mottled 

 appearance ; these lobes are probably the true testes, the flatter 

 central portion would seem to be more or less hollow, and to serve 

 as a vesicula seminalis, as well, probably, as an organ secreting 

 some fluid to increase the quantity of the spermatic material ; at 

 all events the walls are very thick and glandular. 



The coalescing of the testes into an unpaired organ is of course 

 common amongst the Arachnida, e. g. Phalangium ; it also 

 reminds one considerably of the arrangement in Homarus, and 

 in Pleuroma and other free-living Copepoda, &c., among the Crus- 

 tacea, and in insects a very close approach is to be found among 

 the Lepidoptera, as in Pontia hrassicse, &c. ; but if the flatter 

 central portion acts also as a vesicula seminalis this would 

 apparently be a departure from the crustacean type. Nicolet draws 

 the testis in Damseus geniculatus as being four oval, free bodies, 

 on each side, not imbedded in any flat central portion. I am not 

 able to account for this ; certainly, when they are seen through 

 the dorsal surface in transparent specimens, or seen after the noto- 

 gastral shield has merely been removed, they might be mistaken. 



It may of course be suggested that the raised oval portion is 

 the true testis, and that the central portion has some hepatic or 

 other function, and not that of a vesicula seminalis ; but the absence 

 (as far as I have been able to ascertain) of any ducts except the 

 vasa deferentia, and the fact that they lead out of the flat portion, 

 and the intimate way in which the whole is fused into one mass, 

 would seem to negative such a view. 



The vasa deferentia are substantial tubes of moderate length, 

 not longer as a rule than the testis itself; there is one on each 

 side, springing from the anterior part of the flat portion, close to 

 the raised oval (plate II. fig. 1, c), and passing downward, and 

 slightly forward, until they join, and open into the ductus ejacula- 

 torius ; they have a great resemblance to the paired vasa deferentia 

 proceeding from the unpaired testis in the above-quoted case of 

 Pontia hrassicfe. As a rule they are retracted towards the surface 

 of the testis. There is but little variety in these organs in the 

 species which I have dissected. 



The ductus ejaculatorius. — The two vasa deferentia unite, as 

 before stated, at their distal extremities, and are continued by 

 an azygos duct considerably larger in diameter, but short ; it 

 is usually slightly invaginated, like the finger of a glove, and 

 wrinkled longitudinally, so that it is capable of comparatively con- 

 siderable extension and contraction. It is shown in plate II. 

 fig. 1, d. 



