REVIEW OF SPENGEL’S MONOGRAPH ON BALANOGLOSSUS. 417 
that he does not appear to have convinced himself of the truth 
of his own theory, because in discussing possible affinities of 
the Enteropneusta with the Echinoderms, he admits that there 
is a strong resemblance between the larvee, and proceeds even 
to suggest homologies. He believes that the collar pores may 
correspond to the two madreporic pores which have been 
observed in the larva of Asterias by Field.!| Here again, how- 
ever, Professor Spengel’s imperfect understanding of what has 
been done in other groups has misled him. Neither Bury’ nor 
Field has, as he imagines, described a transitory right hydro- 
cele. Bury distinctly states that he regards the hydrocele as 
a structure which has been from the first unpaired ; he does 
describe a right anterior ccelom as well as a left, but the left 
anterior ccelom is not the hydrocele. The oldest larva 
described by Field did not show a trace of the hydroceele, though 
some of the younger possessed two madreporic pores; but it 
is now a dozen years since Ludwig; proved that the madreporic 
pore primarily opens into the ccelom, and that its connection 
with the hydrocele is secondary. The most interesting 
feature of Enteropneustan development is the strong resem- 
blance to the Echinoderm larva which Tornaria presents, which 
renders at least plausible the suggestion that the Protochor- 
data and the Echinoderms diverged from a common bilaterally 
symmetrical pelagic ancestor. On what other grounds besides 
the illusory resemblances of their larvee does Spengel ask us to 
base our belief on a distant affinity between Enteropneusta and 
Annelids? On the assertion that the collar celom is segmented 
from the trunk ccelom, like a mesoblastic somite from the ger- 
minal band of Annelids (this, as I have already said, is an 
assumption contradicted by both Bateson and Morgan), and on 
the direction of circulation in the dorsal and ventral vessels. 
It is surely not going too far to say that a zoologist who 
1 Field, ‘“‘ The Larva of Asterias,” ‘Quart. Journ. Micr. Sci.,’ 1892. 
2 H. Bury, “Studies in the Embryology of Echinoderms,” ‘ Quart. Journ. 
Mier. Sci.,’ 1889. 
3 Ludwig, “ Entwickelungsgeschichte der Asterina gibbosa,” ‘Zeit. fiir 
wiss Zoologie,’ Bd. xxxvii. 
