698 MR FRANK J. COLE 



the first head, to more or less fuse with it. The posterior division (below) is formed 

 in the sections by the fibres of this second head + the superficial fibres of the 

 principal head. Also new fibres are contributed internally which arise from the 

 internal fascia of the latter. The fibres of the first head pass straight forwards, almosi 

 parallel at the la tero- ventral margin of the mouth, and opposed to the external surface 

 of the basal plate until they reach the region of the fourth tentacle, where they are 

 shuffled into two fairly large bundles. One of these, the posterior division (cp. t. c'.) 

 takes an upward bend, and passes at once on to the root of the fourth tentacle just 

 above where the latter is connected by a horizontal ligamentous sheet with the pad of 

 soft pseudo-cartilage at the anterior end of the external bar of the anterior segment of 

 the basal plate. As shown in figs. 3, 9, and 11, the fourth tentacle rests on the 

 external surface of the ventral region of this muscle, and some of the external fibres 

 passing up to it may have a separate origin from the external fascia of the principal 

 head. A variable number of fibres arise from the cartilage of the fourth tentacle 

 itself, and fuse with the posterior division, thus constituting another small head for 

 the muscle. The posterior division now passes upwards, forwards, and inwards, and 

 joins with a bundle arising from the anterior surface of the root of the third tentacle, 

 and coursing straight upwards. This bundle in dissections only seems to accompany 

 the posterior division, and not to fuse with it. In another specimen there was a second 

 and posterior bundle arising from this tentacle. The anterior one (i.e. the one above) 

 was certainly independent of the posterior division, and the posterior one also seemed 

 distinct from, although closely opposed to it. This point is difficult to determine in 

 transverse sections, but in a series of longitudinal vertical sections I find the head 

 from the third tentacle comprised of anterior and posterior bundles as above, which 

 were closely opposed to the posterior division at their insertion, but certainly did not 

 fuse with it. These bundles, therefore, do not, strictly speaking, constitute further 

 heads of the copulo-tentaculo-coronarius, but form small independent muscles like the 

 coronarius, the function of which will be to move the third tentacle in the longitudinal 

 vertical plane. 



Both the posterior division and the bundle or bundles from the third tentacle are 

 inserted into the lateral labial at the place where this receives the cartilage of the 

 third tentacle, the latter into the ventral surface, and the former, which is related to 

 the coronarius, as elsewhere described, into its outer ventral and inner surfaces, and also 

 into the posterior surface of the root of the third tentacular cartilage itself. 



The anterior division, or Tentacularis anterior of P. Furbringer (cp. t. c".), passes 

 forwards and upwards, largely internal to the posterior division, and internal to the 

 fourth and third tentacular cartilages. It is not mentioned by J. Muller in 

 Bdellostoma. It gives off at its origin a bundle of fibres which passes upwards to the 

 posterior surface of the third tentacular cartilage (cp. fig. 3), and its ventral surface 

 is reinforced by some fibres which arise from the root of the fourth tentacular cartilage, 

 and which therefore represent another small head of the copulo-tentaculo-coronaris. 



