392 



THE ARACHNOIDAE. 



§§ 317, 81 o 



J. Hermaphrodite Arachnoidae. 



§ 317. 



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

 the posterior halt" of the digestive canal and opening into the cloaca. This 

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

 narrower, seminiferous tubes, together with the excretory orifices of a 

 pyriform seminal vesicle. With Milnesium, Emydium, and Macrohiotus 

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

 solid epid^^vniis which is detached during the moulting, — so that all the 

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

 Macrohiotus shield their eggs in another manner, by surrounding each 

 with 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 



(2) 



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. 

 374), and O. F. Miiller (in Fue.islu, Arch. d. In- 

 sektenkunde, Hft. VI. p. 27, Taf. XXXVI. fig. i, 5) 

 had already observed that the Tardigrada deposit 

 their eggs in their cutaneous enrelope.* 



1 With tlie Gamasea, and Ixodea, the vulva is sit- 

 uated on the tliorax ; while, with the Trombidina, 

 Bdella, Hydrachnea, and Oribatea, it is upon the 

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

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

 Sc. Nat. XXV. PI. XIV.; J. MiUter, Nov. Act. Nat. 

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

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

 ovaries and oviducts of the Acarina, we have only 

 the works of Treviranus,\eTra. Schrift. I. p. 47 T:if 

 VI. fig. 32 E. q.(Trombidu/7n), and Zeitsch. f. Phys- 

 iol. IV. p. 190, Taf. XVI. fig. 7, 8, 10, a- K. (Ixodes). 

 I have observed with Ixodes ricinus the following 

 peculiarities, which were probably overlouked by 

 Treviranus with Ixodes americaniis. The two 

 long ovaries anastomose areuately at tlie jiosterior 

 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 

 caecum 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. The 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 

 Hydrachnea, 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 Dujar- 

 din (.\nn. d. Sc. Nat. III. p. 20) goes too far in 

 saying that, with 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 vivijjarous and have a large vulva which 

 can be cl(jsed by two lateral alae, and before which 

 is an orifice closed also by a similar apparatus. 

 Tliis last orifice belongs to a tube which Dnjardin 

 regai'ds 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' 

 p/iora, 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 example, Hydrachna ; see Dugis Ann. d. 

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

 under the name of Hydrachna concharuin or Lim- 

 nochares anodontae, and which lives in the cavity 

 of the mantle of Anodontae, buries its eggs deeply 

 in the skin of that oi-gan ; see Pfeiffer, Naturg. 

 deutsch. Land u. Siisswasser-Jlollusk. Abth. II. 

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

 p. 590, Tab. XXI.X. 



* [ § 317, note 1.] See also Kaufmann (loc. 

 (At. \n Siebold and /To/Me?'.? Zeitsch. III. 1851, 

 p. 220), who has studied the development of the 



eggs from their first stages, in the ovary of Macro- 

 bius Dujardin. — Ed. 



