S92 



THE ARACHNOI-DAE. 



S^^ 317, 318. 



/. Hermaphrodite Arachnoidae. 



§ 317. . 



The Tardigrada have only a single, but large, ovarian tube, applied oa 

 the posterior half of the digestive canal and opening into the cloaca. This 

 last which is only a dilatation of the rectum, receives, also, two lateral, 

 2iarrower, seminiferous tubes, together with the excretory orifices of a 

 pyriform seminal vesicle. With Milnesium, Emydium, and Macrobiotus 

 ursellus, the eggs are surrovmded by a smooth chorion, and deposited in a 

 solid epidermis which is detached during the moulting, — so that all the 

 eggs are finally contained in this envelope. But the other species of 

 Macrobiotus shield their eggs in another manner, by surrounding each 

 Tvith a very solid, granular capsule.'^* 



II. Female Arachnoidae. 



' § 318. 



The female organs of the Acarina consist of two ovarian sacs, the ovi- 

 <ducts of which open in a common vulva situated in the middle of the belly, 

 •or further forwards on the thorax, sometimes between, sometimes behind 

 the last' two pairs of legs.'^^ With many of these animals, the oviduct 

 opens into a protractile ovipositor by the use of which the eggs are lodged 

 under the epidermis of plants or animals.'-' A great number of Mites 



1 For the genital organs of the Tardigrada, see 

 Doyire, loc. cit. p. 350, PI. XIII. XIV. XVI. 

 Goeze (Bonnet, Abhandl. aus d. Insekt. 1773, p. 

 .S74), and O. F. Müller (in Fuessly, Arch. d. In- 

 sektenkunde, lift. VI. p. 27, Taf. XXXVI. fig. 4, 5) 

 had already observed that the Tardigrada deposit 

 -their eggs in their cutaneous envelope.* 



1 With the Gamasea, and I.wdea, the vulva is sit- 

 uated on the thorax ; vrhile, with the Trombidina, 

 Bdella, Ilydrachnea, and Oriliatea, it is upon the 

 belly ; see Treviranus, Verm. Schrift. Taf. V. 

 ■{Hydrachna and Trombidium) ; Audouin, Ann. d. 

 Sc. Nat. X.XV. PI. XIV.; J. Midler, Nov. Act. Nat. 

 Cur. XV.Tab. LXVII.; and Treviranus, Zeitsch. 

 f. Physiol. IV. Taf. XVI. fig. 2 (Ixodes). For the 

 ovaries and oviducts of the Acarina, we have only 

 ihe works of TreviTanus,^ erm. Schrift. I. p. 47 Taf. 

 A'l. fig. 32 E. (\. {Trombidium), and Zeitsch. f. Pliys- 

 iol. IV. p. 190, Taf. XVI. fig. 7, 8, 10, \. \. (Ixodes). 

 I have observed with Ixodes ricinus the following 

 X)eculiarities, which were probably overlooked liy 

 Treviranus with Ixodes americanus. The two 

 Jong ovaries anastomose arcuately at the posterior 

 extremity of the abdomen. The two oviducts, here 

 given off, open right and left into a pyriform uterus 

 ■whose neck communicates laterally with a large 

 /;aecum coming from the vulva. This caecum is 

 divided by a septum into a posterior, or larger, and 

 an anterior, or smaller, portion. The first receives 

 the sperm which flows from the second during cop- 

 ulation, and thence passes into the uterus and even 

 into the oviducts. Tlie anterior portion represents 

 the vagina properly speaking, and is in communi- 



cation with two short cylindrical glands filled with 

 transparent cells, and which secrete probably a, 

 substance for enveloping the eggs. I have, more- 

 over, found with other Acarina (for example,with the 

 Ilydrachnea, Gamasea, and Oribatea) various or- 

 gans belonging to the genital apparatus, but without 

 perceiving their relations as clearly as with Ixodes. 

 However this may be, I am convinced that Diijar- 

 din (Ann. d. Sc. Nat. III. p. 20) goes too far iu 

 saying that, witli most Acarina, the eggs are devel- 

 oped loosely in the parenchyma of the body, with- 

 out the necessity of an ovary with proper walls. 

 According to this same naturalist (Ibid.), the Oriba- 

 tea are viviparous and have a large vulva which 

 can be closed by two lateral alae, and before which 

 is an orifice closed also by a similar apparatus. 

 Tills last orifice belongs to a tube which IJujardin 

 regards as a penis ; so that the Oribatea would be 

 hermaphrodites. As to the first point, — the vivipar- 

 ity of these animals, I have verified it for HoplO' 

 phora, Zetes and Oribates ; but I cannot say as 

 much of the second point, for, as I have satisfied 

 myself, the posterior orifice is an anus, and the 

 anterior a vulva having an ovipositor. 



^ For exami)le, Hydrac/ma ; seeDuffis Ann. d. 

 Sc. Nat. I. p. 165. A parasitic mite long known 

 under the name of Hydrac/ma conckarum or Litn- 

 nockares anodontae, and which lives in the cavity 

 of the mantle of Anodontae, buries its eggs deeply 

 in the skin of that organ ; see Pfeiß'er, Naturg. 

 deutsch. Land u. Susswasser-Mollusk. Abth. II. 

 p. 27, Taf. I.; and Baer, Nov. Act. Nat. Cur. XIII. 

 p. 590, Tab. XXIX. 



*[§ 317, note 1.] See also Kaufmann (loc. eggs from their first stages, in the ovary of Macro 

 JUL in Sie ho Id and A'üW/Aef's Zeitsch. III. 1851, Uus Dujardin. — Ed. 

 p. 220), who has studied the development c* the 



