336 Thos. II. Montgomery. 



My observations would show that the segments of the pedipalps and 

 legs arise almost synchronously in accord with most of the preceding 

 work, while Balbiani held that the segments of the third and fourth 

 legs appear later than the other thoracal segments, and Morin held 

 that they developed in order from behind forward; there seems to 

 be no good evidence for Morin's view, nor yet for Lendl's contention 

 that a segment appears between the cheliceral and the pedipalpal. 

 My results are in agreement with those of Balfour and Pappenheim, 

 and in opposition to all others, that the mesoblast of the head lobe is 

 separated from that of the cheliceral segTnent before appendages 

 appear. My views uphold also that of Croneberg, that the rostrum 

 has paired origin and is to be considered a pair of true preoral 

 appendages. But, with most other observers, I agree that there are 

 no other true cephalic appendages; the ''antennae" of Jaworowsky 

 seem to be simply basal portions of the chelicera, composing what is 

 a temporary maxillary plate; and the "head tubercles" of Pokrowsky 

 evidently correspond to the walls of the anterior and posterior lateral 

 vesicles of the head lobe, which are ganglionic formations. Certain it 

 is that there are not more than one ])Siir of coelomic sacs within the 

 head lobe, anterior to the cheliceral sacs. 



If the attempt be made to institute a comparison with the Crus- 

 tacea, then the chelicera of the arachnids might be considered homol- 

 ogous with the second antennae of the crustacean, for both arise 

 postoral then move in front of the mouth, and this view was expressed 

 by Korschelt and Heider (1892) ; therefore, the rostral appendages 

 of the arachnid, which are preoral in position, might correspond with 

 the first antennae of the crustacean. 



14. Segmentation and Appendages of the Abdomen. 



The abdomen grows in length rapidly, after the early thoracal 

 segments have appeared, by teloblastic growth, and its segments 

 appear successively from its anterior end backward. The posterior 

 caudal lobe is a true telson. Eight segments are developed anterior to 

 the caudal lobe, but at reversion the three posterior segments fuse 

 with this lobe. Of these segments the second to the fifth inclusive 

 develop limb buds, the first pair becoming the lung books and the 



