ACARINA. 5 



_ 



9. The venomous organs, which are rarely deficient here, are 



pairs of twisted glandular tubes, which lie and open in the claws 

 of the anteuneal jaws in the head, and only in the caudal style 

 of the scorpions. Probably only the wounds of scorpions are 

 fatal to man ; the utmost that any other Arachnidan can do is to 

 produce a little fever or local irritation, as for example, the 

 Tarantula and Malmignatte. 



10. The sexual organs in the female are racemose or tubular 

 ovarian sacs, lying anteriorly in the abdomen, with short oviducts 

 opening into the vagina, and at the orifice of this, with two 

 horny seminal pouches and an ovipositor. The sexual organs of 

 the male are still very little known. The testes are convoluted, 

 glandular cseca, or racemose vesicles, which open at the extremity 

 of the abdomen. The mites and geometric spiders have a long, 

 horny penis, spines, and a clasping apparatus. In the true spiders 

 the palpi are thickened, and have a spiral thread and horny 

 pieces (hooks, cups, or saucers) in and upon them, with which 

 the males take up the semen and put it into the vagina. 



11. Some mites and scorpions are viviparous; the other 

 Arachriida lay roundish and often large eggs, with a germinal 

 vesicle and simple germinal spot when within the oviduct. The 

 germ-stratum gradually grows backwards over the yelk. The 

 higher species change their skins without any metamorphosis ; 

 the lower ones with a simultaneous metamorphosis. Here the 

 feet are at first undeveloped, without joints, or in smaller number 

 (two or three pairs in mites), elongated, and swollen at the anterior 

 part in the form of a button. After the first moulting the missing 

 pair of feet makes its appearance. The young of the water mites 

 pass into a pupa state during the moulting. Linguatulce lose 

 their feet in the later period of their life. 



The Arachnida are divided into, 1, the Spider-like, in which there 

 is always a distinct separation of the abdomen from the cepha- 

 lothorax, or even of the head from the thorax and a coecal 

 intestine ; the skin is soft ; and, 2, the Crustacea-like with the 

 skin hard, shield-like ; the intestine straight ; the palpi generally 

 nipper-like. 



Order I. ACARINA (Mites}. 



Acarina sunt animalia parasitica, minima, simplicissima ; capite, 

 thorace, et abdomine in unlearn massam confusis ; pedibus in statu 



