30 



ARACHNIDA. 



chitinous structures in the proboscis. There is no mention of an 

 external aperture to the proboscis; Metschnikoff could not find one, 

 although he assumes that the larva obtains its nourishment by 

 sucking the blood of the mother. Soon after becoming attached to 

 the body of the mother, it swells considerably, and becomes filled 

 with a clear fluid (cf. Fig. 17 A and B). If this fluid comes from 

 outside, we must certainly assume that an intestinal epithelium has 

 already developed round the inner yolk-mass, although no such 

 differentiation has been recognised. 



° c o on -J.oO°°^ °A< 



Fig. 17. — Embryo and larvae of Chclifcr (after Metschnikoff, from Balfour). A, embryo in 

 the egg-integument ; B and C, larvae taken from the ventral surface of the mother. «f>, 

 abdomen with the provisional appendages; un.i, anal invagination; ch, chelicerae ; pd, 

 pedipalps ; between the last two {ch and yd) the upper lip is visible in C. Above the pedi- 

 palps are seen, in A the rudiment, in B the base, and in C the last vestige of the proboscis. 

 In l! the rudiment of the oesophageal ganglion can be recognised, lying dorsally to the 

 proboscis. The pedipalps are followed posteriorly by the four limbs, and, in 11, by the 

 rudimentary abdominal appendages. C represents the larva just undergoing ecdysis. 

 The larval integument is partly loosened (noticeably on the ventral side) ; the remains of the 

 proboscis are attached to it. 



The later stages (Figs. 16 and 17 B) differ from the youngest 

 larvae (Fig. 16 A) in external form chiefly in the swollen nature 

 of the dorsal region, brought about by the presence of the clear 

 fluid mentioned above. Other modifications have also taken place, 

 the rudiments of the first pair of limbs having budded out behind 

 the pedipalps, and these are followed by the three other pairs 



