E. IJIPERIALIS. — GEN. CHARACTERS. 61 



a near relationship between the two. As iu that species, the 

 tubuhir body usually exhibits a simple, horn-like curvature, more 

 or less pronounced according to individuals (PL I). However, 

 nearly straight forms or those only slightly bent in S-like or 

 irregular curves are by no means uncommon among the larger 

 specimens. 



The body is approximately circular in cross-section. This 

 is at any rate constantly the case with the basal portion of the 

 body ; the upper portion may show certain irregularities in this 

 respect. When quite full-grown the body is broadest at the 

 upper end and gradually narrows below towards the bulbous 

 basal tuft (PL I, fig. 1). In less advanced stages of growth, 

 however, the shape is that of a slightly bellied tube, the broadest 

 part being situated at or near the middle (figs. 2 & 3) ; otherwise, 

 the breadth remains nearly the same from the broadest portion 

 upwards to the upper extremity. It is clear that after a 

 certain period of life, the growth concerns the upper region 

 only, the lower portion admitting of little or no growth on 

 account of the soldering together of the main skeletal ele- 

 ments, and that the continued growth in girth at the upper end 

 after the growth in length has ceased, finally converts the original 

 bellied tube into the cornucopia-like shape broadest at the top. 

 Thus, the specimen shown in fig. 2 would have yet to grow 

 broader in the upper region in order to attain the definitive 

 shape, such as that of fig. 1. I may say that up to the stage 

 when the body has grown to a length of about 300 mm., the 

 shape of a bellied tube is invariably retained. Not unfrequently, 

 the body considerably exceeds that length — in some cases reach- 

 ing nearly oOO mm.- — without deviating from the shape just re- 

 ferred to ; while, on the other hand, others (e. g., specimen D 



