124 DEVELOPMENT OF THE ANOPLA. 



differentiation of the cutaneous textures. Externally it is coated with long cilia, by aid of which 

 it executes rapid motions, a tuft anteriorly having the form of a long whip-like process, and 

 resembling a single mobile thread during the progress of the animal. The outline is sometimes 

 pitted at the origin of the latter, while a slight papilla projects at the posterior end. When fixed 

 between glasses the cilia are soon thrown off, and the body resolves itself into a number of 

 cells and granules (Plate XXI, fig. 8). In two days the animal is somewhat elongated (Plate 

 XXIII, fig. 14), and the mouth (a) is in the form of a strongly ciliated slit placed nearly in 

 the centre of the body, which, with the above-mentioned exception, is still uniformly granular. 

 A longer tuft of cilia at the anus is now more evident. Two days later considerable 

 increase has occurred in the length of the body (Plate XXIII, fig. 15), and from the anterior 

 position of the mouth, it is apparent the chief increment has taken place in the posterior region. 

 The outline is now pear-shaped, the snout being much less tapered than the tail. The cutaneous 

 textures are more distinctly marked, and the cells, with their refracting contents, very apparent ; 

 there is also a corresponding advance in the growth of the granules of the alimentary canal, 

 its ciliation, and the posterior sacculations. The whip-like tuft on the snout is somewhat 

 shorter, and there now exist a few longer cilia on the side of the head, the posterior group of 

 which (c) are evidently the precursors of the long ciliary tuft, which by-and-by appears. There 

 is yet no trace of eye-specks. A few cylindrical papillae are observed on the snout and tail, 

 and one or two along the sides, which processes do not seem to result from pressure. A day or 

 two afterwards some are furnished with one and others with tw r o eye-specks ; moreover, the tuft 

 of cilia on the snout is gradually diminishing, while the lateral cilia (c) before mentioned are 

 becoming longer. During a period stretching from March to the beginning of June, the various 

 vessels swarmed with successive broods of young (from different individuals), which in the form of 

 minute white specks darted about most actively. They did not crawl along the bottom, but, like 

 the young of Vhyllodoce and other Annelids, swam freely throughout the water after the manner of 

 Infusoria, or danced to and fro like Ephemera in the air. Externally at this further stage of 

 advancement they still have a coating of very long cilia (Plate XXIII, fig. 16), which serve as 

 natatory organs, the tuft (c) on each side being about thrice as long as the rest, while the anterior 

 whip has disappeared. There are two large well-defined black eyes, no doubt provided by nature 

 for the exigencies of the youthful state, just as the young of certain mollusks and cirripedes are 

 similarly furnished. The mouth («), the oesophagus, and succeeding region of the digestive 

 cavity are all richly ciliated. The whole animal is soft and delicate, and few of my specimens 

 survived this stage. Those which outlived the others became more elongated, and had a little 

 reddish pigment developed in the snout. After the disappearance of the eyes (in October) they 

 have the form of slender reddish bodies, with a conspicuous mouth a short distance behind the 

 anterior margin. The cilia on the snout are very much longer than on the rest of the body, and 

 project like a long brush or fan, so as to give the animal the aspect of an infusorial animalcule. 



We have thus in Cephalothrix a certain resemblance to the development of M. van Beneden's 

 Nemertes carcinophila, already described (see p. 93), and the phases of the growth of the present 

 species likewise corroborate everything that has been advanced in contradistinction to the inter- 

 pretations of the Belgian author. His views in regard to the scolex and proglottis receive no 

 support from the foregoing observations, for all the changes that occur are only the gradual and 

 very perceptible shedding of certain cilia, and the general advance in organization as shown by 

 the differentiation of tissues and the appearance of pigment in the eye-specks. The moulting of 



