THE ARACHNIDA. 43 I 



mark off the cephalo-thoracic from the abdominal region. The 

 integument may be seen to be forming in the abdomen, and the 

 rudiments of the heart or dorsal blood vessel are noticed. The 

 eyes begin to be distinguished. The diminution of bulk in front 

 continues during the ninth period, and the division into two 

 parts also. The chest and abdomen become more defined and 

 elongated. The legs now present slight traces of a division 

 into joints, and have increased greatly in size and length. 



Tenth period. The small end of the ovum, which is still 

 more elongated, is now found to be distinguished from the large 

 one by a true constriction dividing the ovum into two parts, 

 denominated in the perfect spider, thorax and abdomen. The 

 visible parts of the thorax are the mandibles, the palpi, and the 

 legs. These latter appendages are folded upon the chest, and 

 have grown so long as to cross the middle line of the body, 

 and they are locked together like the fingers when the hands 

 are clasped. The abdomen presents nothing remarkable except 

 an elongated opaque streak, which exists along the middle of 

 the under surface from the feet to the end of the belly. Heroldt 

 considers this to be an indication of the development of the 

 internal parts of the abdomen, of the intestinal canal, and the 

 secreting organs. In proportion as the young spider increases, 

 the external membrane or covering of the &g^ is applied more 

 exactly to its body, and seems to represent an exterior skin, of 

 which the young creature soon divests itself almost in the same 

 manner as the caterpillar sheds the skin in which it is enveloped. 



By the increase of the young creature during this last stage 

 of all, the membrane of the tg^ becomes so stretched, and is 

 applied so exactly to the surface of the body, that the different 

 parts of the body can be seen through it like the nymph or 

 chrysalis of certain insects. The essential parts of the thorax 

 are the head and feet. The head is of a white colour, and is 

 surmounted by eight brown streaks ; the legs, which are also 

 white, are closely applied to the chest, with their extremities 

 alternating with each other. One may distinguish in each a hip, 

 a thigh, a leg, and a tarsus. The articulations of the palpi and 

 mandibles are also visible through the general envelope of the 

 tg%. The streak upon the abdomen has divided, and part of 



