57 
In Proneomenia, where I expected to find that the branchial ap- 
paratus could be more easily studied because of the larger size 
of the specimens I was very much surprised to find that a similar 
structure is altogether absent, or at least of so very much smal- 
ler dimensions that it cannot possibly be as efficacious as in Neo- 
menia. The posterior and inferior walls of the anal cavity (into 
which the rectum widens out) are covered with a folded epithe- 
lium, but no separate branchial chamber nor an increase in size 
and number of these folds and projections of the epithelium, into 
which blood might penetrate and by which respiratory processes 
might be facilitated, can be detected. This is the more striking 
because the size to which the apparatus attains even in the small 
specimens of Neomenia renders any oversight in Proneomenia of 
similar organs quite impossible.e. An apparent arrangement of some 
of these folds into a shallow lateral chamber in one of my speeci- 
mens (and on one side only) is most’ probably due to an accidental 
folding of the walls. So we must come to the conclusion that respi- 
ration is provided for in another way, and indeed, the sur- 
faces all along which the blood may come into contact with more 
or less pure seawater are numerous and extensive. The surfaces 
alluded to are: 1) the whole of the intestine, where a vast mass of 
blood is only separated from the seawater contained in it by not 
more than one layer of cells, partly ciliated. This surface is considerably 
augmented by the deep folds of the intestinal walls, between 
which the blood freely and copiously eirculates, 2) the eiliated 
folds bb’ of figs. 17 & 29 and perhaps also the curious bundle of 
hollow tubes p all of them present in the mouth cavity beneath 
the lipfold {. In the interior lacunae of the ciliated folds blood- 
corpuscles were decidedly met with; 3) the whole length of the 
foot in which blood-corpuscles that fill it and that may serve at 
the same time towards its distension and extrusion are again only 
separated by one layer of ciliated cells from the external seawater; 
4) and finally the strongly folded surface of the reetum which is 
beset with extremely strong eilia (two to three times the height of 
the cells) and the folds of which are again more thickly filled with 
