420 BE. W. MACBRIDE. 
Fic. 134.—Diagram of two “ inner gill-pores ” of Balanoglossus (Ptycho- 
dera), showing their skeletal structures and the relation of the latter to the 
slits. Br. sep. Gill septum. 
Fic. 134.—Similar diagram of three complete gill-slits of Amphioxus. 
Lr. sl. Gill-slits. 
Fic. 14a.—Diagram showing the extent to which the gill-sacs are developed 
in a vertical direction in Balanoglossus (sensu stricto). 
Fig. 144.—Similar diagram of gills of glandiceps. 
Fic. 14c.—Ditto, ditto, Schizocardium. 
Fic. 14d.—Ditto, ditto, Ptychodera. 
PLATE 30. 
Fic. 1¢.—Diagrammatic transverse section of Amphioxus larva, showing 
the division of ccelom into splanchnocele and myoccele, the hollow sclerotome 
and its relation to the notochordal sheath. 
Fie. 14.—Similar section of Balanoglossus. Ch?. The mesoblastic sheath 
of ‘‘chondroid tissue.” 
Fic. 1e.—Similar section of the Scyllium embryo. Sc/. The sclerotome, 
here a solid outgrowth from the wall of the myocele. 
Fic. 2.—Ptychodera minuta. Dorsal aspect. G. p. Outer gill-pores. 
Magnification 2. 
Fig. 3.—Ptychodera erythrea. Dorsal aspect. Natural size. 
Fie. 4.—Glandiceps Lachsi. Dorsal aspect. Natural size. 
Fic. 5.—Schizocardium brasiliense. From the side. 
Fic. 6.—Balanoglossus Kowalevskii. Magnification +. 
Fic. 7—Balanoglossus Kupfferi. Natural size. 
Fic. 8.—Collar skeleton of Ptychodera minuta. 
Fic. 9.—Collar skeleton of Balanoglossus Kupfferi. #. Head. W. 
Wings. B. Body. JZ. Crura. 
Fic. 10.—Collar skeleton of Ptychodera aurantiaca. 
Fic. 11.—Collar skeleton of Schizocardium brasiliense. 
Fig. 12.—Collar skeleton of Balanoglossus Kowalevskii. 
Fie. 13.—Collar skeleton of Schizocardium peruvianum. 
