Observations on the Orihatidse. By A. D. Michael. 15 



The duct, even when full of eggs, continues to be plicated 

 longitudinally, so that the eggs, when in situ, often appear to lie 

 at the side of the body, one over the other in a bunch ; this 

 however is a deceptive appearance, they really follow each other in 

 single file along the duct. The ova sometimes lie end to end, 

 sometimes obliquely across the duct, sometimes almost side by 

 side (through the stretching of the duct) ; the position of the 

 eggs in the duct is very irregular, I have not ever seen them all 

 following one another end to end at regular distances, and regularly 

 increasing in size from the first to the last, as figured by Nicolet, 

 although the end to end arrangement is not unusual in the species 

 he figures. 



These oviducts are what Nicolet calls the ovaries, and what I 

 term the ovipositor is named oviduct by him ; I regret using the 

 words in a different sense, but in the first instance it seems to me 

 that his term is scarcely correct, although very natural, he not 

 having observed the central ovary ; and in the latter case, although 

 the organ is unquestionably an oviduct, as far as the derivation of 

 the word goes, yet it appears convenient to distinguish it by a 

 name different from the duct between the ovary and the vagina. 



The vagina, if this be a correct name for an organ which 

 probably does not receive the male one, is a short but wide azygos 

 duct, into which the oviducts lead ; it is manifestly the homologue 

 of the ductus ejaculatorius, and is of similar consistency to the 

 oviducts of which it forms the continuation. It appears to vary 

 but little in the different species which I have investigated ; its 

 ofi&ce is to conduct the eggs from the oviducts to the commence- 

 ment of the ovipositor. The egg does not remain in the vagina for 

 any length of time. 



The ovipositor, or external vagina of Burmeister, has been 

 described by me in a former publication, and one form of it is well 

 figured by Nicolet. I therefore shall not repeat it here ; the same 

 thing applies to the genital suckers and plates. 



Nicolet figures the female reproductive organs of Bamseus 

 genioulatus more on the insect type than the crustacean, i. e. 

 without the central ovary above named, treating my oviduct as the 

 ovary, and drawing it as diminishing to a point at each side, with 

 the eggs regularly increasing in size from the distal point to the 

 vagina. I have not found any specimen in this condition. 



It is necessary here to notice a remarkable error, as to the 

 reproductive organs of Orihatidse, for which Dujardin is responsible,* 

 but which has somehow retained a place in modern English 

 works of authority.! The usually keen-sighted French naturalist 

 started with the initial error that the Orihatidse were viviparous : 

 he, having this idea in his mind, did not consider that they could 



* " Premier memoire sur les Acariens," Ann. des Sci. Nat., 3rd ser. iii. p. 5. 

 t Rymer Jones' ' Animal Kingdom,' 4th ed. p. 309. 



