170 SIDNEV F. HARMER. 



EXPLANATION OF PLATES XVI & XVII, 



Illustrating Mr. S. F. Harraer's Paper on "The Life-history 



of Pedicellina," 



Reference Letters. 



an. Anus. an.c. Anal cone. a.v}a.nA a.v? Hypothetical morphologically 

 anterior and posterior ends, respectively, of the vestibular aperture, a. v. v. 

 Aperture between oral and anal divisions of vestibule (in position of permanent 

 mouth), b. Bud. br. Brain (= "dorsal organ"), c. c. Fragments of 

 ciliated cells, c. p. Ciliated pit of brain, c. r. Ciliated ring. d. s. Dorsal 

 sense-organ (of Loxosoma). epst. Epistome. /. br. Pibrous part of brain. 

 /. ,^. Foot-gland, ffa. Ganglion of adult, ff. p. Growing point of stolon. 

 ff. V. Median groove of permanent vestibule, ultimately becoming the vesti- 

 bular aperture (in position of part of oral groove of larva ?). int. Intestine. 

 I./. Lateral fold of vestibular wall. I. v. Lateral portions of anal division of 

 vestibule, m. Mouth, mes. Mesoderm. m. v. Median postanal portion of 

 the anal division of the vestibule, m. (Esophagus, o. g. Oral groove. 

 rec. Rectum, s. Sucker, st. Stomach, t. Tentacle, v. Vestibule, v. a. 

 Its aperture, v. an. " Anal " division of vestibule, v. or. " Oral " division. 

 V. V. Ventral division, x. Large-celled tissue at base of epistome and anal 

 coue. 



PLATE XVI. 



Pedicellina echinata. 



Fig. I.— Median longitudinal section of a larva quite recently fixed (on 

 Coralline). 



Fig. 2.— Obliquely longitudinal section (in the plane C D in figs 3 and 4') 

 of a similar larva. 



Fig. 3. — Horizontal section of a slightly older larva, passing through brain 

 (= dorsal organ), oesophagus, epistome, and anal cone. 



Fig. 4.— Obliquely transverse section (in the plane A B in fig. 1), at a stage 

 very soon after fixation. 



1 In describing one section as passing in a plane indicated in the figure of 

 another, it is to be understood that the details in the two individuals do not 

 always exactly correspond. This is due, partly to a difl'erence in age between 

 the two larvse figured, and partly to variations in the position of the internal 

 structures, owing to varying conditions of muscular contraction. 



