120 KltWIN S. noOORICH. 



List op Reference Letters in Plates 8 and 9. 



a. Amis. up. Aperture of the ventral sac. a. t. c. Anterior extension of 

 tiie trunk eoelom. hi. c. Blood-corpuscles. c. s. Cut edge of the septum. 

 c.tt.c. Cut tentacular cceloni. d.bl.v. Dorsal blood-vessel, d. h. Dorsal 

 horn of the pre-septal ccelom. d. w. Dorsal wall of the subneural pocket. 

 ep. Epidermis. /. Mesenchymatous fibres. /I. Flagellum. //. Pre-oral hood. 

 ffl. Nerve ganglion or brain. ?/. Nucleus of the solenocyte. nepk. Nephri- 

 dium. neph.p. Nephridiopore. neph. c. Nephridial canal. nv. Anterior 

 nerves to the pre-oral ring. or.s. CEsopliagus. pa. c. r. Perianal ciliated 

 band. pa. s. Perianal sinus, po. c. r. Pre-oral ciliated band. ^w. c. Pre- 

 septal eoelom. po. ps. h. Pre-oral, pre-septal blood-space, or haemoccel. ps. h. 

 Pre-septal hsemoccel. ;•. Ridge of stomach wall. s. Septum, sn.p. Sub- 

 neural pocket, s.pa. Septum closing off tiie perianal sinus, st. Stomach. 

 &lr. Mesenchymatous strands, t.c. Trunk eoelom. tl. Tentacle, tt. ccel. 

 Tentacular eoelom. tt.h. Tentacular liajmoccel. tt.b. Base of tentacle whicli 

 grows into the adult tentacle, v. c. Vascular csecum. v. d. Ventral diverti- 

 culum of the stomach, v.s. Ventral invaginated sac. v. v. Ventral blood- 

 vessel, w. VV'^all separating the pre-septal hsemocoel from the ccRlom. 



EXPLANATION OF PLATES 8 and 9. 



Pigs. 1 — 8, 10, 13 — 15 represent the larva; from Faro. 

 Figs. 9, 11, and 12 represent a larva from Trincomalee. 



Fig. 1. — Diagrammatic reconstruction of an Actinotrocha larva drawn as a 

 solid object cut along a sagittal plane a little to the right of the middle line so 

 as to avoid the median ventral mesentery. The pre-septal blood-cavity {ps. h.) 

 is continuous with the pre-oral blood-cavity (po.ps. //.) round the sides of the 

 Nubneural pocket {sn.p.). The pre-septal coelomic canal (/j.f. r.) is seen cut 

 through twice. The hsemorrel is continued backwards beyond the septum as 

 a narrow slit along the mid-dorsal and the mid-ventral line of the stomach. 

 The trunk ccelom {(. c.) is separated from the perianal sinus by a thin con- 

 tinuous epithelium. 



Fig. 2. — Similar view of a larva from which a portion of the left body-wall 

 has been removed, exposing the pre-septal blood-cavity, the pre-septal 

 coelomic canal with its tentacular branches, the ventral invaginated sac in 

 the trunk ccelom, which extends dorsally, pushing the septum with it {a. t. c), 

 and the ventral mesentery. The inner blind end of the ncphridium, provided 

 with solenocytes, is seen projecting into the pre-septal blood-cavity. The 

 external cilia are not represented. 



