50 



ARACHNIDA. 



Long before 



d-~ 



B, and 26), which may lie so far apart that the yolk protrudes 

 between them (e.g., Agalena, Balfour, Fig. 29, p. 53). Anteriorly, 

 in the cephalic lobes and also at the caudal end, the two halves of 

 the germ-bands remain united (Figs. 28 A and B, 26). 



the germ -band has divided to such an extent, 



the rudiments of the limbs- 

 have appeared, the first to be 

 seen being those of the four 

 pairs of ambulatory limbs, as 

 slight prominences a little re- 

 moved from the median groove 

 (Fig. 28 A, 3-6). These are 

 followed by the rudiments of 

 the pedipalps (2), and, a little 

 later by those of the cheli- 

 cerae (1). The rudiments of 

 limbs arise in the same way 

 on the first four abdominal 

 segments (Figs. 28 A, a, 27), 

 so that the abdomen of the 

 embryo is not only much more 

 fully segmented than that of 

 the adult, but even has limbs 

 on some of its segments. In 

 this respect the Araneae re- 

 semble the Scorpiones, which 

 also have limbs on the ante- 

 rior abdominal segments (p. 8). Further similarity is found in the 

 fact that, in the former, the posterior part of the abdomen may be 

 flexed forward ventrally like the post-abdomen of the Scorpion 

 embryo. This is the case in Pholcus, as was pointed out by 

 Claparede, and confirmed by Emerton, Schimkewitsch, and 

 Morin. 



It is almost universally admitted that the first four abdominal 

 segments carry provisional appendages (Balfour, Locy, etc.). Even 

 Morin's researches, carried out by the help of the latest methods, 

 yielded the same result, although Salensky had mentioned a first 

 limbless segment, and Schimkewitsch had accepted this view. The 

 statements of these two authors are supported by the notes and 

 figures of Bruce, published after his death (No. 54). We were able 

 easily to convince ourselves, by examination of an Araneid embryo 



Fig. 2ij. — Embryo of Phrfcus opilionoides, ideally 

 unrolled (after Claparede). ch, chelicerae ; 

 d, yolk ; kl, cephalic lobes ; ped, pedipalps ; 

 Pi~Pt, first four pairs of limbs ; 1-3, first three 

 abdominal segments ; pah, the posterior part 

 of the abdomen flexed ventrally. 



