316 
The original number of eyes on the ocular tubercle was almost 
certainly only one pair. In Mygale, there are more than one pair on 
a tubercle, which may or may not be the primitive ocular tubercle. 
In the majority of Arachnids, the accessory eyes are arranged along 
the edge of the new dorsal surface formed by the cephalic lobes. It is 
necessary therefore to assume that they have been independently 
acquired, a fact borne out by the striking structural differences they 
present. Whereas according to Lankester and Bourne? the lateral 
eyes of Scorpio have the retinal cells arranged so that their distal ends 
are in contact with the lens, without the intervention of a vitreous 
body, I have recently shown? that in the Chernetidae the retinal cells 
are inverted, and their large nucleated ends are in contact with a very 
well developed hypodermal, or vitreous layer. 
On turning to the embryos of the Arachnida, we have the re- 
markable procephalic lobes above alluded to. Unfortunately little is 
known of the embryology of Galeodes. In the embryo of the Araneids, 
the cephalic lobes are very conspicuous and pass through a stage in 
which they might almost represent a »head« like that in Galeodes 
(Fig. 3). 
In the embryo of Scorpio, these lobes lie in front of the mouth, 
an arrangement simply due to their displacement by the yolk. They 
are early laid down, and develop on each side of the mouth and pro- 
stomium, eventually taking part in the formation of the dorsal sur- 
face. As nearly as can be expected, they repeat the phylogenetic 
development above described. 
I think thus that the head of Ga/eodes throws a new light on these 
enigmatical procephalic lobes, and on the morphology of the anterior 
segmentation of the Arachnids. The interesting formations and mark- 
ings found by Jaworowski5 on the cephalic lobes of Trochosa re- 
quire some other interpretation than that which he wishes to attach 
to them, as there could hardly have been any true antennae in front 
of the chelicerae. 
If the interpretation of the »head« of Galeodes here put forward 
is correct, we have to look upon the retention of it as a primitive fea- 
ture of equal importance with the segmented cephalothorax which 
characterizes the Galeodidae. 
3 Q.J. M. S. Vol. XXIII. 
4 Journal of the Linnean Soc. (in the press). 
5Jaworowski, Zool. Anz. T. XIV. 1891 and May 1892. 
