634 PROFESSOR E. RAY LANKESTER. 
In his ‘Manual of the Anatomy of Invertebrate Animals’ 
Professor Huxley has recognised the possibility of the rela- 
tionship of Limulus to Scorpio as well as to Copepoda, and 
has also instituted a comparison between the appendages of 
Limulus and those of the Podophthalmous Crustacea. 
He considers only one pair of appendages of Limulus to 
be innervated from the cerebral ganglion, and regards the 
chilaria as the seventh pair of appendages, whilst he asso- 
ciates the genital operculum (his eighth pair of appendages) 
with the cephalothoracic carapace instead of with the 
abdominal carapace. In these respects recent investigations 
have necessitated a change of view (as I have explained at 
some length above), and accordingly the comparisons based 
upon the earlier view of the facts are erroneous. Thus, 
Huxley identifies the first pair of appendages of Limulus 
with the antennules of Astacus, and regards it as absent in 
Scorpio. The second pair he identifies with the antennee of 
Astacus and with the cheliceree of Scorpio, the third pair 
with the mandibles of Astacus and with the great chel of 
Scorpio, the fourth and fifth with the two pairs of maxille 
of Astacus and with the two first walking legs of Scorpio, 
the sixth (the digging leg) of Limulus with the first 
maxillipede of Astacus and the third walking leg of Scorpio. 
The chilaria or metathoracic sternites, which are considered 
by Huxley as the seventh pair of appendages, he identifies 
with the second maxillipedes of Astacus and with the fourth 
walking leg of the Scorpion, whilst the genital operculum is 
identified with the third pair of maxillipedes of Astacus and 
with the genital operculum of Scorpio. 
The comparison of Limulus with the Podophthalmous 
Crustacean appears to me one which, in reality, it is not 
possible to carry out so as to establish any identities, or 
plausible points of contact. Even when we reckon the 
“ chilaria”’ as appendages we find divergence and difference 
as the result of the comparison ; but when these are removed 
from the series there is an absolute want of any relation in 
the grouping of the appendages compared. Not so with 
the Scorpion. Professor Huxley, in consequence of his view 
as to the nature of the chilaria, is obliged to assume that 
the chelicere of the King Crab are something over and above 
what is present in the Scorpion, and thus, eventually, in 
counting down the segments, he brings the genital operculum 
of the one into coincidence with that of the other. But 
when the chilaria are removed from the series offered by 
Limulus there is no need to assume an existence of extra 
appendages in front in that animal; the whole series in 
