63 
clustering of the eyes, the distinctness of the group, the superficial 
location of the eyes, and their larger size afford full security as to 
homologization of these eyes with the tentacular eyes of other 
Acotyleans. The conclusion can then be safely drawn that the 
Acotylean type of tentacles, i. e. nuchal 
tentacles, originally belonged to Emprostho- 
pharynx. To-day it is merely expressed 
in the interruption of the muscular wall 
and the retaining of the superficial loca¬ 
tion of the tentacular eyes. 
It is a common feature that the 
tentacles or the tentacular area, when the 
tentacles disappear, are nearly totally devoid 
^of giand cells in the epidermis. Thus the ten¬ 
tacular epidermis shows usually a striking 
contrast to the ordinary gland-bearing epider¬ 
mis of the body. This distinguishing feature 
is, however, of little value here, as the 
-whole d or sal body surface is rather poor 
,as to giands. The demarcation of the ten¬ 
tacular rudiments Emprosthopharynxm the 
epidermis is thus less apparent, as a glance 
■at the photograph mentioned will prove. 
; Epidermis. The dorsal epidermis is 
certainly lower than the ventral one, but 
the difference in height is never considerable. Through the pre- 
servation the epithelial cells are somewhat shrunken and thus 
slightly isolated from one another. This condition affords excellent, 
clear images of the cellular elements in the epidermis. It verifies 
^my earlier description of the epidermis of the Polyclads. The sup- 
porting cells (= „Deckzellen“) exceed to a very great degree all 
;other kinds in the dorsal epithelium. On the ventral side the 
giand cells producing rhabdites occur in extremely great numbers. 
They are absent in the adhesive zone, which receives rhabdites 
i from the parenchyma (cf. Bock 1913, pag. 163). The large nuclei, 
rich in chromatine, reach half the length of the cell-body. Their 
;Shape (rounded to oval) depends on the contraction State of the 
i 
muscular wall of the body, as the height and breadth of the cells 
Text-fig. 18. Emprosthopha- 
rynx opisthoporus Bock. 
Outline of a specimen, with 
pharynx, main intestine, 
large ventral nerve trunks, 
and tentacular groups of 
eyes indicated. 
