136 Kart WILHELM GENTHE, 
rows of bristles which adorn the sides of the head. This line 
extends ventrad some distance and can be traced to a spur-like 
chitinous thickening projecting inward at the base of the oral cirri. 
Something like this line is given in Berxpr’s fig. 1, but the whole 
region appears so unlike what I see in my preparations that the 
identification sometimes becomes difficult. This portion of the animal 
looks, of course, different in different preparations according as the 
muscles which connect the body with the disk are more or less 
contracted. With the state of the muscles the animal changes its 
position within the mantle. Therefore its angle with and distance 
from the lips of the Jatter and from the region of the projecting 
knob-like point of attachment of the disk; the two tooth-like pro- 
jections ventrad from this knob, and the region of attachment of 
the body to the disk, they all present entirely different aspects. 
Fig. 8 which shows the line in question well (as do many others 
of my preparations) represents an animal which was carefully freed 
from the mantle and mounted in glycerine. In this one (as in 
others) another trace of segmentation appears just where the muscles 
pass from the disk etc. into the body of the animal. This segmen- 
tation, however, I admit is not so distinct and, moreover, can be 
made out only occasionally, for in most cases this region is more 
contracted and the strong muscles hide everything underneath. 
I should like to take the two marks of segmentation as the 
lines of the first thoracic segment (Fig. 8 J) limiting it to this 
narrow region and, if that seem gone too far, call certainly the 
more distinct cranial one the separation of head and thorax. The 
mantle then would appear rather as an evagination from the thorax 
than from the head. If this view be acceptable the disk at once 
cannot be regarded any more as homologous with the stalk of the 
Lepadidae as AukiviLLıus thinks it. My view agrees to an extent 
with Brrnpr’s who says the disk has to be considered as ~an 
evagination of the carinal (dorsal) portion of the mantle and by no 
means as an elongation of the head portion like the peduncle of 
the Zepadidae. The larval antennae, if they were preserved in 
Alcippe, would be found not on the distal portion of the disk nor 
in the centre of it but near the dorsal end of the lips of the mantle 
where the body connects with the mantle. This problem can be 
solved only when the right stage of development will have been 
found. 
In the following portion of the thorax the segmentation is very 
