Plate XXIX. 



(F/'f/fi. Ö8-G0 nrp drcuoi from Jnrvœ Jjrlouf/hu/ io fijpe D). 



Fig. öS {a-e). — These figures show different parts of a larva of 44 t(^ntacles. 

 Figure a sliows a cross section throngli the iiioutii, h throngli the 

 middle portion of the oesophagus (œ.s-.) ; magnified x '2 ]î ; c a 

 portion of a cross section of the stomach wall (dorsal) and the 

 trunk walls, x 2 F. d and e show respectively a longitudinal and 

 a transverse section of a tentacle (the former magnified x 2 D> 

 the latter x 4D). 



Figs. 59 (d-d). — Four cross sections taken from a series, not consecutive, 

 and tlieir respective planes of section are given in the text with 

 reference to the woodcut (p. .")42). Unfortunately in these series, 

 the tissues have undergone a great disturbance by the killing reagent, 

 but the relations of the layers remain essentially correct, and those 

 spaces whicli have lieen produced from the mutual splitting of the 

 layers are denoted by " artefact." x 2 D, 



Figs. 60 (a and b). — -Eepresent the nervous system of Acthiotrocha (of 

 type B), revealed ])y vital staining with methyl blue and ammonium 

 molybdate. In a, as the larva was ])ressed by the coverglass, the 

 rim which a])pears like the free margin of the hood is not that 

 edge at all, but rejiresents the line along which the hood was 

 bent by jiressure ; the line drav/n near the peri[)heral blue dots is 

 th(^ true edge of the hood, h shows a portion of the free margin of 

 the hood, where the nerve fibres end. c/ x 4 B, & x 2 F. 



Figs. Gl {n and l). — Are taken from serial sections of a A-\\\\e larva 

 which bears the evaginated pouch ; a shows four blood corpuscles, b 

 one portion of the wall of the stomach diverticulum. x 2 F. 



Figs. G2 (o and />). — Taken from serial transverse sections through the 

 nephridial region of the adult, b shows the inner and of the left 

 nephridial canal where the smaller funnel (_/"') is attached. 



