dlO SUPPLEMENT 



The number of feet is usually eight. Some, however, have 

 but six, and the females of some others have two more, which 

 only, however, answer the purpose of carrying the eggs. 



Most of the arachnida subsist on living prey, or suck the 

 blood, or other fluids of several animals. 



The sexual organs of the females, and even in many of the 

 males, are situated at the base of the belly, or near its junc- 

 tion with the thorax. They are double in most of the pul- 

 monary arachnida, and perhaps in all. The males of the 

 araneides, or spinning arachnida, have theirs at the extremity 

 of the palpi; a character which indicates the natural affinity 

 between these animals and the last order of the Crustacea. 



The araneida do not undergo any essential change of 

 form, and are only subject to moulting. In some, however, 

 two of the feet are not developed, until some days have 

 elapsed from their birth. It is only after the fourth or fifth 

 change of skin, that these animals become adapted for the 

 purposes of generation. 



Most of the pulmonary arachnida are suspected, or dreaded, 

 as being venomous. The bite or incision made by some of 

 them may produce, under some circumstances, and more 

 especially in warm climates, accidents of a serious nature. 



The body of the araneides, or spinning arachnida, is com- 

 posed of an inarticulate trunk, with which the head is con- 

 founded, and the abdomen fixed to the posterior extremity 

 of the trunk by a small thread. It is usually soft, without 

 rings, or with nothing but folds, and having from four to six. 

 external nippies placed under the anus. These nipples are 

 a sort of spinnerets, and exist in both sexes. 



The trunk is crustaceous, and presents, at its anterior part, 

 a triangular space, which appears to correspond with the 

 head, and on which the simple eyes are situated. These 

 organs evidently replace the composite eyes of the insects, 

 and are always six or eight in number. Their size and dis- 



