WILLEY ON THE ENTEROPNEUSTA. 
MAYNARD M. METCALF. 
Dr. ARTHUR WILLEy has made such valuable contributions 
to our knowledge of the morphology of the lower Chordata that 
it is with high expectations one opens his recent memoir upon 
the Enteropneusta. He describes in considerable detail many 
points in the anatomy of three species of Ptychodera (two of 
them new), of two species of Spengelia (one new), and of a 
Tornaria, all from the South Pacific, and also describes as new 
and distinct species belonging to the genus Ptychodera two 
West Indian forms, from Bimini (in the Bahamas) and from 
Jamaica. This anatomical part of the memoir is full of details 
of considerable interest to the student of the Enteropneusta, 
but hardly of such a nature as to permit description in this 
review. The author's observations, however, serve him as a 
foundation upon which to rest some very far-reaching theo- 
retical conclusions, and to these it may be profitable to direct 
attention, referring to so much of the anatomy as may be 
necessary for a correct understanding of the basis for these 
conclusions. 
Willey’s first proposition is that “the gonads and gill slits 
were primarily unlimited in number and coextensive in distri- 
bution, the gonads having a zonary disposition and the gill slits 
Occupying the interzonal depressions. The primary function 
of the gill slits was the oxygenation of the gonads, their sec- 
ondary function being the respiration of the individual.” In 
Support of this contention that in the lower Chordata the series 
of gonads once extended much further forward, while the series 
of gill slits extended much further backward, the gill slits lying 
between the gonads and serving chiefly for their oxygenation, 
: * Willey, A. Zovlogical Results. Pt.iii, Enteropneusta from the South Pacific, 
with Notes on the West Indian Species. Cambridge, University Press, May, 1899. 
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