220 



PART II. SYSTEMATIC ACCOUNT 



shield is divided into front and back halves by a slight transverse groove 

 (Fig. 14). 



The length of the whole animal, excluding the tentacle, is up to 9-6 cm, 

 while the breadth of the body reaches 0-25 mm. If it is stretched out the 

 tentacle may reach from 13 to 25 mm in length, depending upon the degree 

 of contraction. The anterior part of the body is 1-0-1-8 mm long. 



In the living animal the body is more or less transparent, so that the blood 

 vessels, filled with red blood, are clearly visible. 



The spindle-shaped spermatophores, 

 round in cross-section, taper gradually 

 towards one end (Fig. 113), and from 

 the slightly broader end an appendix 

 continues into the base of the extra- 

 ordinarily long and slender filament. 

 The spermatophores are 0-18 mm long. 

 The ringed tube is semi-transparent 

 and very flexible. In a fresh condition, 

 and also after fixation in formalin or al- 

 cohol, it appears greenish to the naked 

 eye or under a hand lens, but under 

 higher magnification the tube is brown- 

 ish. The rather dense, brown regular 

 rings are about half to two-thirds the 

 diameter of the tube in length (Fig. 

 11 1£), but exceptionally one may come 

 across rings considerably shorter. They 

 are separated by light transparent inter- 

 vals of the same length, which consist of 

 a softer material; transverse wrinkles 

 often appear on their surface and then 

 they become considerably shorter. For 

 a considerable distance the front part of 

 the tube lacks rings. It is here com- 

 pletely transparent, colourless, very 

 flexible and usually flattened into a sort 

 of ribbon (Fig. 85). The walls are mem- 

 branous in this part, then, passing back- 

 wards, the tube runs into the ringed 

 portion. The hindmost part of the tube, 



Fig. 113. Siboglinum 

 caulleryi: Spermatophore 

 (After Ivanov, 1957a.) 



