8 MICROSCOPICAL STUDIES. 



Fig. 3. Normal Colleto-cystophore, x 17. 



Figs. 4, 5 & 6. Abnormal series of same, X 17. 



Fig. 7. Abnormal tentacle, showing shortening and thickening of 



peduncle, x 17. 



Fig. 8. Group of normal tentacles, x 30. 

 Fig. 9. Developing ovum, in optical section, x 25. 



STUDY II. THE PELAGIC ANNELID TOMOPTERIS. 



Occasionally among the contents of the tow-net there appears 

 this tiny paddle-propelled worm, active and sprightly in movement, 

 and so glassy and colourless as to be well nigh indistinguishable from 

 the water it moves in. The species figured on Plate I. averages 

 scarcely J-inch long, but its breadth seems very great in proportion 

 owing to the great length of the paddle-like feet or parapodia. The 

 head is very distinct. At the front border are two stout gracefully 

 curved antennae (a), while just behind these is a pair of very delicate 

 processes (a 1 ) which have also been called antennae. Next come the 

 most conspicuous appendages in the body a pair of enormously 

 elongated tentacular cirri (t c.) In the centre of each one, and sup- 

 porting it, is a stout bristle, seen under a high power to be septate 

 (Fig. 13). Following these, about thirteen pairs of paddle-shaped 

 parapodia entirely destitute of setae, and consisting of a hollow cylin- 

 drical basal portion, expanding at the outer or distal end into two 

 foliaceous blades upper and lower which represent respectively, 

 the notopodium and the neuropodium of the typical annelid foot. 

 Every foot is controlled by two principal sets of muscular fibres 

 originating close to the median line in the body wall, one passing 

 obliquely forwards to be inserted in the anterior border of the foot, 

 the other backwards to the posterior border. 



The mouth is situated between the tentacular cirri and leads 

 into a rather muscular portion, capable of at least partial extrusion 

 as a proboscis (Carpenter). This passes through a short oesophagus 

 into a long and wide stomach, reaching nearly the whole remaining 

 length of the animal. The body cavity is quite continuous. There 

 are no internal septa and the interior of the parapodia communicates 

 freely with the body cavity. The chief development of the nerve 

 system consists of a large anterior ganglionic mass, seated upon which 

 are two eyes, each composed essentially of a pigmented cushion 

 bearing two crystalline cones. In front of each eye is a large vesicle 

 of unknown function. 



The sexes are separate. That depicted is a female and shows 

 how the ovaries arise from the growth of certain cells on the inner 

 surface of the peduncles of the parapodia. These cells grow to a 



