19 



Fig. 33, which is a sagittal section through the body and collar, shews no trace of the connexion 

 of the two parts of the proboscis which are seen respectively anteriorly and posteriorly, with 

 the rest of the animal. 



These curious phenomena are due to the great length of the neck (figs. 23, 24, 139), 

 which can be twisted into almost any position, either by being simply bent out of the median 

 plane, or by being not only bent but also twisted round its own longitudinal axis. In buds and 

 young blastozooids, and in some of the old zooids, the position of the proboscis is normal; that 

 is to say, as in other species of Ccphalodisctis. A case of this kind is represented in fig. 34. 

 The neck here appears short and thick, though indications are not wanting, in the folding of 

 the dorsal epidermis, that a considerable amount of contraction has taken place. It is not difficult 

 to imagine that the basal, cylindrical portion of the proboscis in fig. 34 could, during life, be 

 considerably elongated, and the discoidal portion rotated round an angle of 180° so as to bring 

 the pigmented line to the dorsal side and the real dorsal portion of the disc to the ventral 

 side. This is what has taken place in PL IX, fig. 10 1 and in PI. XI, fig. 139. If the rotation 

 be not so complete, — for instance, if it extend only to 90°, — the pigment-line assumes a 

 more or less longitudinal position, as in several of the zooids seen in fig. 11. In the reconstructed 

 individual .shewn in figs. 23, 24 the elongated neck extends straight forwards, the discoidal 

 portion looking in the same direction. This individual exhibits another phenomenon which is of 

 common occurrence in this species, though something of the same kind may also take place in 

 C. dodecalophus. By special contractions of the strong muscles which extend from the septum 

 dividing the first from the second body-cavities, part of the glandular anterior epidermis of the 

 proboscis may be deeply infolded. Sections of the proboscis of individuals in which this has 

 taken place are sometimes difficult to interpret. 



In the individual shewn in fig. 33 the neck is simply bent to one side, so as to have 

 a direction at right angles to the median plane. The lateral portions of the mantle-like proboscis, 

 with the ends of the pigment-band, have thus in this sagittal section a relation which they 

 should normally have in a transverse section. 



The arrangement of the body-cavity of the proboscis materially helps in the interpretation 

 of sections of this species. Here, as in all other cases, the body-cavity extends to the extreme 

 dorsal end of the organ (figs. 34, 42, etc.), where it is spacious; while it invariably di.sappears 

 before the pigment-band is reached. The ventral lobe of the proboscis consists of a double 

 layer of epidermis, the layer next the mouth being very thin, but the two layers are in close 

 contact with one another without being separated by any part of the first body-cavity. 



It should further be noted that the mobility of the neck in C. levinseni begins in front 

 of the notochord and of the septum between the first and second body-cavities. Thus in the 

 sagittal section, fig. 33, in which the anterior part of the neck is bent entirely out of the median 

 plane, the symmetrical position of the central nervous system [c. n. .y.),. of the notochord {nch.) 

 and of the pericardium {per.) has been in no way affected. 



There are six pairs of arms in C. levinseni, as in C. dodecalophus; but I have not 

 observed any indication of vesicle-bearing end-bulbs in the adults or at any stage in the growth 

 of the buds. 



