No. 3-] LOXOSOMA DAVENPORT!. 355 



Study of the living animal. If a number of specimens in clear 

 sea water in a smooth glass vessel be observed attentively, 

 individuals may often be seen lying on the dorsal surface with 

 the lophophore fully expanded. If a current of water from 

 a pipette be directed against an animal in this position, it 

 becomes evident at once that the creature is attached quite 

 firmly by the lophophore margin ; and though the foot end may 

 be lifted up by the motion of the water, the hold of the animal 

 is loosened only by a very strong current. This observation 

 makes it evident that the cells in question serve as a means of 

 attachment. They are to be regarded as unicellular suckers, 

 which are of use to the animal by enabling it to keep a hold 

 upon its host while changing its foot attachment. The pro- 

 jecting saucer-shaped portion of the cuticula probably serves 

 as a disc for attachment, and the lines traversing the cytoplasm 

 as differentiations enabling the cell to contract in one direction, 

 perpendicular to the surface. Harmer ('85) described certain 

 large cells in the margin of the lophophore of L. tethyae, and 

 considered them glandular in function. That they are homolo- 

 gous with those which I have found in L. Davenporti seems 

 extremely probable, and renewed investigation may be expected 

 to show a similarity in function. 



When the body is in a contracted condition, the lateral mar- 

 gins protrude on either side as thin outfoldings of the body- 

 wall or alae, which are represented in transverse section in 

 PI. XXXII, Fig. 2. In PI. XXXII, Fig. i, the alae are repre- 

 sented as they appear from the ventral side in a partially con- 

 tracted individual. In the fully expanded condition (PI. XXXII, 

 Fig. 11) no trace of them is to be seen. Similar alate ex- 

 pansions of the body have been described by Schmidt ('76) 

 for L. raja (= L. Neapolitanum Kow.) and by Prouho ('91) for 

 L. annelidicola. In the latter species they appear to be much 

 more prominent structures than in L. Davenporti. 



In the median line of the posterior side of the body is a 

 peculiar row of prominent cells shown in PI. XXXII, Figs. 2, 

 7, and 8. These cells are very noticeable, both in the living 

 animal and in preserved specimens. They are sharply set off 

 from those upon either side, and are arranged with perfect 



