REVIEW OF SPENGEL’S MONOGRAPH ON BALANOGLOSSUS. 395 
able to support with so little inconvenience serious truncations 
ofits posteriorend. A further interesting point is that neither 
proboscis nor collar is able to function unless it is turgid, 
and that it is impossible for it to attain this turgidity even 
when placed on a moist substratum if it is out of water. 
Hence it is probable that water is taken in through the pro- 
boscis and collar pores to set up this turgidity. This strik- 
ingly recalls a point in Echinoderm physiology. The only 
function which it is possible now to ascribe to the stone canal 
and madreporic pores, in view of the fact that the current in 
them is inwards,! is the maintenance of the turgidity of the 
water-vascular system. 
The fact that the currents through the proboscis pore and 
the collar pores probably set inwards is not, as Professor 
Spengel points out, irreconcilable with the fact observed by 
Bateson, that carmine introduced into the proboscis cavity is 
ejected by the pore, since the contraction of the muscular wall 
on the fluid contents must necessarily cause ejection of the 
latter, together with any particles of an excretory nature which 
they may contain. 
Fig. 9 shows us how the muscles of the anterior face of collar 
radiate from the skeletal rod, the more ventral fibres forming 
loops. The somatic wall of the collar cavity has an outer layer 
of circular muscles only on its anterior half; its muscles are 
mainly longitudinal. The splanchnic wall has an inner layer 
of longitudinal muscles. In the more primitive species these 
are gathered in front into a single bundle and inserted in the 
divergent crura of the skeletal rod; in other species only the 
more dorsal have this insertion. The circular muscles of the 
splanchnic wall are derived from a forward diverti- 
culum of the trunk celom, which Spengel calls the peri- 
pharyngeal cavity. There is one on each side of the buccal 
cavity, and their relations to each other and to the perihemal 
cavities are shown in figs. 4 and 10 (P. PA). 
The chief point to notice in the trunk muscular system is 
1 Ludwig, H., ‘Uber die Function der Madreporenplatte der Echino- 
dermen,” ‘ Zool. Anzeiger,’ No. 339, 1890. 
