REVIEW OF SPENGEL’S MONOGRAPH ON BALANOGLOSSUS. 419 
Gen. R. Genital ridge. H¢. Heart. Hé. aur. Auricular prolongations of 
heart of Schizocardium. Hy. Br. Hypobranchial epithelial band of Schizo- 
cardium. Zi. Liver saccules. JZ. S. Lateral septum of trunk celom.. M. 
Mouth. Muse. Muscular fibres. Myce. Myocele. P. C. Pericardium. P. C. 
Aur. Auricular prolongations of pericardium of Schizocardium. P. #. Peri- 
hemal space. Pph. Peripharyngeal space. Pr. Proboscis. Pr. Ce. Pro- 
boscis celom. Pr. Cw. V. Ventral pocket of proboscis celom. Pr. P. Pro- 
boscis pore. Pr. vm. Ventral mesentery of proboscis celom.  Proct. 
Proctodeum. Sc/. Sclerotome. Sp. Cw. Splanchnocele. Stom. Stomodeum. 
Sy. Synapticulum. 7. B. Tongue-bar. Zr. Trunk. Tr. ce. d. Dorsal 
division of trunk celom. 77. ce. v. Ventral division of the same. 77. d. m. 
Dorsal mesentery of trunk celom. 77. v. m. Ventral mesentery of trunk 
celom. V. NV. Ventral nerve-cord of trunk. V.V. Ventral blood-vessel. 
PLATE 29. 
Figs. 3, 4, and 5, and Figs. 8—14 inclusive, are taken from the monograph, 
though in some cases simplified in detail. 
Figs. 2—13 inclusive are copied directly from the monograph. 
(All figures diagrammatic.) 
Fic. 1.—Horizontal longitudinal section of Balanoglossus. 
Fic. 2.—Sagittal longitudinal section of Balanoglossus (Ptychodera). 
Fic. 3.—Transverse section of proboscis region. 
Fic. 4.—Transverse section of collar region. 
Fig. 5.—Transverse section of branchiogenital region. 
Fie. 6.—Horizontal longitudinal section of embryo of Balanoglossus 
Kowalevskii, according to Mr. Bateson. 
Fie. 7.—Ideal sagittal section of developing Tornaria, illustrating Professor 
Spengel’s theory of the formation of the mesoderm. 
Fic. 8.—Illustrates arrangement of fibres in the longitudinal muscular 
layer of the proboscis. 
Fig. 9.—Illustrates arrangement of fibres in the circular muscular layer of 
the anterior wall of the collar cavity. 
Fic. 10.—Sagittal section of collar region, showing mutual relations of 
collar ceelom, trunk ccelom, perihemal and peripharyngeal spaces. 
Fics. 1la, 114.—Transverse sections of trunk, showing insertion of lateral 
septum. Fig. 11a is behind the gill region ; Fig. 114 is in the hinder part of 
the gill region. 
Fries. 12a, 4, c, d, e.—A series of five transverse sections through the 
anterior part of the notochord and adjacent pericardium and heart in Schizo- 
cardium. 
VOL. 36, PART 3.—NEW SER. FF 
