386 E. W. MACBRIDE. 
against the view now so widely accepted as to the Vertebrate 
affinities of the group. 
Before entering on the new points contained in the mono- 
graph it will be necessary to give a rapid sketch of the history 
and the extent of our present knowledge of the anatomy and 
development of Balanoglossus. Kowalevsky! was the first 
who gave a tolerably correct account of the anatomy. Our 
knowledge on this point was almost completed by Professor 
Spengel’s? preliminary account. in 1884. Between the years 
1884 and 1886 Bateson’ contributed a series of papers on the 
development and morphology of Balanoglossus, which laid 
a solid foundation for the interpretation of the anatomical 
facts as indicative of Vertebrate affinities. Quite recently 
Morgan‘ has published a paper on the growth and develop- 
ment of Tornaria, which entirely confirms Bateson’s account, 
making allowance for the difference between direct and free 
larval development ; and Marion,’ Schimkewitsch,° and Kohler? 
have given during the last few years descriptions of different 
species. 
Fig. 1, Pl. 29, is a diagram representing a horizontal section 
through an adult. We notice that there are three regions to be 
distinguished in the body, viz. the przoral lobe or proboscis, 
the thick “collar” region, and the trunk. The proboscis 
region is largely filled with muscle, but it also contains a small 
coelomic space opening on the left by a ciliated pore. The 
collar and trunk both contain a pair of such spaces, and the 
1 «Anatomie des Balanoglossus delle Chiaje,” par A. Kowalevsky, in 
‘Mém. Acad. Imp. Sc. St. Pétersbourg,’ 1866. 
2 J. W. Spengel, “Zur Anatomie des Balanoglossus,” ‘Mitt d. Zool. 
Station z. Neapel,’ Bd. v, 1884. 
3 Bateson, ‘Development of Balanoglossus,” various papers, ‘ Quart. 
Journ. Micr. Sci.,’ 1884—1886. 
4T. H. Morgan, “Growth and Development of Tornaria,” ‘Journal of 
Morph.,’ vol. v, 1891. 
5 A. F. Marion, “ Sur deux espéces de Balanoglossus,” ‘ Arch. Zool. Exp.’ 
(2), Tome iv. 
6 Schimkewitsch, ‘“‘ Ueber Balanoglossus Mereschkovski,” ‘ Zool. Anz.,’ 1888. 
7 R. Kohler, “Contributions 4 l’Etude des Entéropneustes,” ‘ Inter. 
Monatsschrift Anat. Hist.,’ Bd. iii, Heft 4. 
