558 SUMMABY OF CUREENT RESEARCHES RELATING TO 



7- Arachnida. 



Poison Apparatus and Poison of Scorpions.* — J. Joyeux-Laflfuie, 

 from his own studies and a consideration of what has been discovered 

 by other naturalists, comes to the conclusion that the poison-organ 

 of the scorpion (S. occitanus) is formed by the sixth or last somite of 

 the post-abdomen, which terminates by a sharp process, at the ex- 

 tremity and sides of which are two oval orifices by which the poison 

 escapes. There are two secreting glands, each of which opens by an 

 excretory duct to the exterior. Each gland is situated in a cavity, 

 which it completely fills, and which is formed by the chitinous 

 skeleton and by an enveloping layer, formed by striated muscular 

 fibres ; it is by the contraction of this latter that the poison is forced 

 out. The gland has a central cavity which acts as a kind of reservoir, 

 and a proper wall, which is formed of a layer of cells that send out 

 prolongations into the cavity, and of a layer of epithelial cells, which, 

 in the fresh condition, have a finely granulated protoplasm ; these are 

 the secreting cells. The poison is very active, and, even in weak 

 doses, soon kills most animals, and especially arthropods or verte- 

 brates. The phenomena of poisoning are always the same, and take 

 place in the following order — (a) pain at the point of injury ; 

 (h) period of excitement ; (c) period of paralysis. The convulsions 

 which are characteristic of the second stage, are due to the action of 

 the poison on the nervous centres, and especially on the brain ; the 

 paralytic phenomena are caused by the action of the poison on the 

 peripheral extremities of the motor nerves, where they appear to 

 have the same influence as curare. The muscles, the heart, and the 

 blood are in no way attacked, and the poison may therefore be cer- 

 tainly placed among those which act on the nervous system. The 

 scorpions found in France (S. europceus and S. occitanus) cannot cause 

 the death of a human subject, and are only dangerous when several 

 poison a man at the same time, or attack very young children. To judge 

 by his bibliography, the author is unacquainted with the observations 

 on the habits of scorpions, published in 1882 by Prof. Lankester. f 



Structure and Function of the Liver of Spiders. | — P. Bertkau 

 finds that the so-called liver of spiders arises by the develop- 

 ment of a considerable number of diverticula of different sizes from 

 the widened portion of that region of the intestine which is found in 

 the abdomen ; as these branch more and more they become united 

 into a continuous whole by the formation of an intermediate tissue. 

 Of the entire diverticula five are larger than the rest, and they are, 

 like the intestine at their point of origin, glandular in nature. The 

 epithelial cells are either small and oviform, closely packed with 

 large colourless spheres, or they are larger and club-shaped, when 

 part of their contents consists of small crystals and larger drops, 

 which are yellow, brown, or green in colour. The chief function of 

 the secretion of these glandular cells is the breaking up and altera- 



* Arch. Zool. Exper. et Gen., i. (1883) pp. 733-83 (1 pL). 



t See this Journal, ii. (1882) p. 612. 



J Arch. f. Mikr. Auat., xxiii. (1884) pp. 214-45 (1 pi.). 



