106 G. A ELRINGTON 



PERSONAL OBSERVATIONS. 



Buccal organ. Passing now to those features in the structure of the 

 larva which hâve been the object of spécial investigation on our part, we 

 would, in the first place, draw the attention of the reader to an organ 

 situated in the floor of the mouth, which we hâve called the buccal organ, 

 FiG. ] and 2. 



On the inner side of the lower lip is a pocket shaped invagination, the 

 mouth of which is placed transversely. The lining of this pocket is not 

 ciliated like the other parts of the mouth, but consists merely ofathin 

 membrane, beneath which is a layer of granules, which are stained deeply 

 by hagmatoxylin. 



Bands of muscle fibres are attached to this membrane and extend in- 

 wards in a perpendicular direction until they meet and become mingled 

 with a circular band of muscle fibres situated a short distance beneath the 

 surface of the invagination. 



The position of thèse two sets of muscle fibres can be seen by referring 

 to FIG. 2. The circular band of muscles extends from the front to the back 

 of the organ, forming with the perpendicular muscles a crescent shaped 

 structure. From the base of the organ, a band of muscle travels backwards 

 and becomes connected with the ventral muscles of the body. 



The outer or anterior cap of the pocket is marked by a strip of columnar 

 epithelium, fig. 2, the cells of which are arranged in a very regular man- 

 ner, and hâve well defined nuclei. Granulations are abundant in thèse cells, 

 particularly near the surface. 



This muscular structure appears to be the foundation of the bilobed 

 buccal organ of the adult Lanice, fig. 3, and other species of Terebellids. 

 Watson ( 1 890) has shown that the neighbouring species Terebella littoralis 

 collects the particles of sand and other materials wherewith it constructs 

 its tube, by means of its tentacles, and draws them towards the prostomium, 

 and thus transfers them to the lips, where they are rolled over within the 

 mouth, and covered with a white transparent cément. During this process 

 a bilobed organ is seen to protract from the lower lip. 



