SPIR0BRACH1A BEKLEMISCHEVI 453 



The rather wide individual variation in their number is, however, very 

 noticeable. Thus in one individual, for instance, there were about 15 such 

 papillae, while in another there were not less than 50. There is no distinct 

 zone of thickened papillae, and all the papillae of the whole preannular 

 region have the same structure, while the plaques of the hinder part of this 

 region are distinguished only by their slightly larger size. 



The considerable predominance of the metameric over the non-metameric 

 part of the trunk in S. beklemischevi is undoubtedly the result of the evolu- 

 tionary process whereby the papillae have become increasingly more ordered 

 in their arrangement (p. 21). It seems likely, moreover, that this feature may 

 be shared by S. grandis, in which, however, the non-metameric part of the 

 trunk has not been observed. 



Two girdles, interrupted ventrally, but continuous dorsally, lie on feebly 

 developed ridges (Fig. \74F, G). The yellowish elongate-oval toothed plate- 

 lets are disposed in two to four rows in each girdle (Fig. 174Я). The front end 

 of the platelets is fractionally narrower than the hind end and the front group 

 of teeth, though not big and occupying only a quarter to a fifth of the area of 

 the whole platelet (Fig. 1747), is well developed. The platelets are 20-25/x 

 long and 6-8/it broad. 



The very long postannular section of the trunk (Fig. 16) usually starts with 

 a sharp waist, which, however, is absent in a few individuals. Behind the 

 girdles there is always a large ventral papilla with a plaque (Fig. 17 4F). 

 Farther back the papillae, which lie only on the ventral side, are concentrated 

 into transverse metameric rows, situated at more or less equal intervals 

 (Fig. 16). There are five to seven papillae in each row, and here and there, 

 between the rows, one may encounter solitary papillae. The plaques here are 

 slightly curved, bow-shaped or rod-like. 



The length of the animal, including the tentacles, may reach 13 cm. The 

 parts of the body have the following dimensions : length of the tentacular 

 crown, 7-10 mm; breadth of the crown, 1-1-3 mm; length of the fore-part of 

 the body, 1-5-4 mm; breadth of the fore-part, 0-75-1-3 mm; length of the 

 metameric part, 48-5-58 mm; length of the non-metameric part, 10-12 mm; 

 length of the postannular region, 40-45 mm; overall length of the body 

 1 17-129 mm. S. beklemischevi is one of the least elongated of the Pogonophora, 

 for its length is only a hundred times its breadth. 



The flat, leaf-shaped spermatophores are much broader at the filamentar 

 end and sharply pointed at the afilamentar end (Fig. 175). The basal part of 

 the filament is rather stout for a considerable length. Around the broad 

 end of the spermatophore extends a cortical zone free from sperm. The 



