Respiration in Invertebrate Animals. 403 



the edges of the respiraton^ laminse : these cilia arc most con- 

 spicuous in P. lamelligera. This is a striking point of distinction 

 between the Phyllodocida and the Nereids, in which cihary epi- 

 thehum has no existence. The chylaqueous liuid then may be 

 clearly affirmed as that agent in the oecouomy of the Phyllodo- 

 cida which is the immediate, the J^rst, subject of the respiratory 

 process, the true blood receiving its supply of oxygen from this 

 fluid, afterwards to convey it to the solid structures of the body. 



In the genus Glycera the blood-proper is entirely excluded 

 from the organs of respiration : this office devolves exclusively 

 on the chylaqueous fluid. The latter in this worm is crowdedly 

 charged with re</-corpuscles, a remarkable exception to the An- 

 nelidan rule. The gills consist of hollow, cylindrical appendages, 

 emanating from the base of each dorsal foot at its superior aspect, 

 filled in the interior with the chylaqueous fluid. It is pecuhar 

 to and distinctive of this genus that the interior of the branchiffi 

 is lined with vibratoiy epithelium. Cilia are not detectible on 

 the exterior of these processes, but they exist in the intei'ior : 

 under the action of these oarlets, the coi-puscles of the chylaqueous 

 fluid by which the gill-process is penetrated, move with great 

 rapidity in a definite dii-ection ; — peripheradly on one side and 

 centradly along the other, each coqiuscle whirling on its own axis 

 as it proceeds. The advancing stream, however, is not divided 

 from the returning. The channel is one, open channel. This 

 is the laic which is applied to the chylaqueous fluid : it knows 

 no exception. Its channels are always single and csecal : its 

 movements a flux and reflux. Contrarily the orbit of the true 

 blood is circ/e-like, its channels closed, its colour red, its compo- 

 sition non-morphotic. 



In the Syllida (fig. 6) the branchial organs are penetrated only 

 by the chylaqueous fluid. It can be detected only at the bases of 

 the feet {d). To this part the vibratile cilia are restricted (c). 

 The long filiform, and in some species moniliform or leafy appen- 

 dages which are described commonly as the branchiae in these 

 worms, have no central hollow ; they are filled with lacunose 

 tissue (/) through which the fluid parts of the contents of the 

 visceral chamber slowly penetrate. But in the spacious cham- 

 bers occupying the bases of the feet, the corpuscles may be detected 

 in whirlpools. From this fact the inference may be drawn that 

 the corpuscles are not essential to the flrst mechanical stage in the 

 respiratory process — that of receiving oxygen dii'cctly from with- 

 out. The characters of stnicture just described are very perfectly 

 typified in S. prolifera, the moniliform variety^ is best seen in 

 S. armillaris and S. maculosa. A similar conformation pre- 

 vails in the genera loida and Psamathe of Dr. Johnston. In 

 the Syllidan family, which excels all others in grace and beautv, 



28* 



