414 E. W. MACBRIDE. 
independent adaptation to burrowing life, since it seems likely 
that the main stem of the chordate phylum retained a pelagic 
life; the highly developed sense-organs point in this direction, 
As to the homology of the atrial fold in Amphioxus with the 
posterior edge of the collar in Enteropneusta, so long 
as we are ignorant of the representative of the collar 
ceelom in Chordata, it must remain merely a tentative suggestion. 
Morgan’s researches: have, however, destroyed one of Professor 
Spengel’s main objections to this comparison, viz. his assertion 
that the collar pore opens into the first gill-slit. With regard 
to the homology of the anterior enteric diverticulum of 
Amphioxus with the proboscis cavity, it is difficult to believe 
that Professor Spengel is serious when he says that the 
proboscis cavity is not asymmetrical, but only the proboscis 
pore, and on that ground objects to its comparison with the 
preoral ceelom of Amphioxus, more especially as, when speaking 
of the Tornaria, he suggests that the proboscis cavity is really a 
left-sided structure, the fellow of which is the pericardium. 
Affinities of Enteropneusta with Annelida. 
As mentioned above, Professor Spengel believes that Balano- 
glossus is distantly related to the Annnelida ; and in support of 
this view he endeavours to show that the Tornaria is a modified 
trochosphere. Now Tornaria shows very great resemblance to 
an Echinoderm larva, so that it was for a long time mistaken 
for one; the only points in which it agrees with the tropho- 
sphere, and differs from all Echinoderm larve, are the possession 
of eye-spots on its apical plate, and the strong muscles running 
from the plate to the esophagus. These latter, however, since 
they are merely differentiations of the przoral celomic wall, 
may be compared to the longitudinal muscles in the przoral 
lobe of Bipinnaria. Hence in order to torture the Tornaria 
into a trochosphere, he finds it necessary to make a series 
of violent assumptions, which are not only not supported by ob- 
servations, but in direct contradiction to such observations as 
we have. In this connection, also, it is impossible to avoid 
expressing indignation at the way in which the results of the 
