392 



THE ARACHNOIDAE. 



S^§ 317, 31 



I. Hermaphrodite Arachnoidae. 



§ 317. 



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

 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, 

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

 pyriform seminal vesicle. With Mihiesium, Emydium, and Macrobiotus 

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

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

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

 Macrobiotus shield their eggs in another manner, by surrounding each 

 with a very solid, granular capsule.'^' 



//. 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 thoi-ax, 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. au3 d. Insekt. 1T73, p. 

 374), and O. F. Muller (in Fuesslv, 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.xodea, the vulva is sit- 

 uated on the thorax ; while, with the Trombidina, 

 Bdella, Hydrachnea, and Oribatea, it is upon the 

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

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

 So. Nat. X.XV. PI. XIV.; J. Muller, 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 Acariua, we have only 

 the works of Treviranus,\eTva. Schrift. I. p. 47 Taf. 

 A'l. fig. 32 E. q.(Trombidium), and Zeitsch. f. Phys- 

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

 I have observed with Ixodes ricinus the following 

 peculiarities, which were probaljly overlooked I)y 

 Treviranus with Ixodes americanus. The two 

 long ovaries anastomose arcuately at the posterior 

 extremity of the abdomen. The two oviducts, here 

 given oiT, 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 (Ann. d. Sc. Nat. III. p. 20) goes too far la 

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

 oped lo isely i?i the parenchyma of the body, with- 

 out the necessity of an ovary with proper walls. 

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

 tea are vivii)arous and have a large vulva which 

 can be closed l)y two lateral alae, and before which 

 is an orifice closed also by a similar apparatus. 

 This last orifice belongs to a tube which Dujardin 

 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~ 

 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, Hydrackna ; see Dugis Ann. d. 

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

 under the name of Hydrackna concharum or Lim- 

 nochares anodontae, and which lives in the cavity 

 of the mantle of Anodontae, buries its eggs deeply 

 in the skin of that organ ; see Pfeijfer, Naturg. 

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

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

 p. 590, Tab. XXIX. 



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

 tXt. \n Sie bo Id and iro^Z/Ae/'s Zeitsch. III. 1851, 

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



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

 bias Dujardin. — Ed. 



