Observations on the Orihatidw. By A. D. Michael. 13 



the paired oviducts, terminating in an unpaired vagina, the ovi- 

 positor, and the copulative suckers and genital plates. 



The ovary, or ovaries, for it is doubtful if they should be treated 

 as paired or azygos, consist of a large central sac or gland, which 

 underlies the ventriculus, in much the same position as that occu- 

 pied by the testis ; this I take to be the true ovary, from the walls 

 of which the eggs are differentiated ; it will be found fully developed, 

 even when the creature has only lately emerged from the nymphal 

 skin, and when there are not any eggs in the oviducts or other 

 genital organs. At this period the walls of the ovary are cellular, 

 the ova being more or less rudimentary (see plate II, fig. 5). At 

 a later period, when the eggs have become developed, and when 

 their formation and deposition is in active progress, the ovary may 

 be seen to contain numerous eggs in a considerably more advanced 

 state (plate II. figs. 6, 7). This central ovary appears to me 

 possibly to consist of two paired organs, which have coalesced in the 

 central line, much in the same manner as the testes. It is true 

 that the ovary of Orihata lapidaria (plate II. fig. 5, a), Oribata 

 glohula, &c., is an elliptical organ, giving little, if any, indication 

 of a dual origin, particularly when immature, but in Ce^heus 

 tegeoeranus (plate II. fig. 6, a), in the mature ovary, there is a 

 decided indication of a paired origin, there being a marked central 

 constriction, and an approach to the outline of the coalesced testes. 

 In Nothrus theleproctus, when the eggs are developed, the ovaries, 

 or portions of an ovary, from the two sides have so slight an attach- 

 ment to each other that they easily separate, and then appear as 

 paired structures, one attached to each oviduct. 



The oviducts. — These, like the vasa deferentia, are two paired 

 ducts, arising, one from near each end of the central ovary ; they 

 are long, membranous tubes, which, before the eggs have commenced 

 to mature, appear empty ; they are then usually corrugated and 

 plicated organs, of about even dimensions throughout ; they are 

 shown in this condition at plate II. fig. 5, h, but it must be under- 

 stood that this and all the other figures of ovaries are drawn from 

 preparations dissected out and partly extended ; when in situ they 

 are so much doubled backward and forward that a drawing of them 

 in their actual position would not give much information. As the 

 eggs are formed, and after they have increased a little in size in 

 the ovary, they pass into the oviducts, where the principal growth 

 takes place. The oviducts seem to perform the function of a uterus, 

 and the passage of the egg through them is consequently very slow ; 

 the eggs will sometimes be found small in the portion of the ovi- 

 duct between the ovary and the globular enlargement mentioned 

 below, and large in that between those parts and the vagina ; at 

 all other times, or in other species, the eggs all appear about the 

 same size, i. e. usually all fully grown. The oviducts mth. the 



