TEACH EAT A. 367 



striction between the future thorax and abdomen. The four pairs of 

 provisional appendages exhibit no signs of atrophy; and the extent of 



FlG. 201. TWO LATE STAGES IN THE DEVELOPMENT OF AGELENA LABYRINTHICA. 



A. Embryo from the side at the stage when there is a large ventral protuberance 

 of yolk. The angle between the line of insertion of the permanent and provisional 

 appendages shows the extent of the ventral flexure. 



B. Embryo nearly ready to be hatched. The abdomen which has not quite 

 acquired its permanent form is seen to be pressed against the ventral side of the thorax. 



pr.l. procephalic lobe ; pd. pedipalpi; ch. chelicerae; c.l. caudal lobe; pr.p. pro- 

 visional appendages. 



the ventral flexure is shewn by the angle formed between the line of 

 their insertion and that of the appendages in front. The yolk has 

 enormously distended the integument between the two halves of 

 the ventral plate, as is illustrated by the fact that, at a somewhat 

 earlier stage than that figured, the limbs cross each other in the 

 median ventral line, while at this stage they do not nearly meet. 

 The limbs have acquired their full complement of joints, and the pedi- 

 palpi bear a cutting blade on their basal joint. 



The dorsal surface between the prominent caudal lobe and the 

 procephalic lobes forms more than a semicircle. The terga are fully 

 established, and the boundaries between them, especially in the abdo- 

 men, are indicated by transverse markings. A large lower lip now 

 bounds the stomodseum, and the upper lip has somewhat atrophied. In 

 the later stage (fig. 201 B) the greater part of the yolk has passed into 

 the abdomen, which is now to some extent constricted off from the 

 cephalo-thorax. The appendages of the four anterior abdominal 

 somites have disappeared, and the caudal lobe has become very small. 

 In front of it are placed two pairs of spinning mammillae. A delicate 

 cuticle has become established, which is very soon moulted. 



