508 PROFESSOR E, RAY LANKESTER, 
has for years been an open secret, which has escaped notice 
by something like fatality. 
B. Comparison oF LimuLus AND Scorpio. 
The Arachnid which comes nearest in structure to Limulus 
is the Scorpion. In some few points the Spiders and, yet 
again, the Phrynidz are more closely similar to Limulus 
than isthat animal. I shall proceed, systematically, through 
a comparison of the skeletal and chief internal organs of 
Limulus with those of Scorpio, pointing out where other 
genera of living Arachnida come into closer agreement with 
the former than does the Scorpion. 
§ a. NERVOUS SYSTEM.—As the view which may be 
adopted in regard to the agreement or distinctness of appa- 
rently corresponding parts in Limulus and Scorpio depends, 
to a considerable extent, on the indications afforded by the 
nervous system, it will be as well to proceed at once to 
state what is now known with regard to that system in 
both Limulus and Scorpio. 
For a long time our knowledge of the nervous system of 
Limulus was very defective, owing to the fact that only 
badly preserved spirit-specimens had been dissected. Hence 
it has been held by Van der Hoeven (11) and by Owen (7) 
that the nerves which supply the first two pairs of appen- 
dages take their origin from a nervous mass in front of the 
cesophagus. Dohrn (1) and Huxley (16), on the other hand, 
have stated that only the nerves to the first pair of appen- 
dages are pre-cesophageal in origin. It was reserved for 
M. Alphonse Milne-Edwards (5) to demonstrate by the dis- 
section of perfectly fresh specimens of Limulus the true 
arrangement of these parts. I am able, from my own dissec- 
tion of a fresh specimen of the same animal, to confirm 
M. Milne-Edward’s description, though I must say that such 
confirmation is a mere formality, since the beautiful memoir 
in which that author has published his results bears through- 
out unmistakable evidence of care and accuracy. 
With regard to the nervous system of Scorpio, we are not 
in the same favourable position. No zoologist, so far as I 
am aware, has studied the nervous system, or, indeed, any 
of the viscera of Scorpio by the aid of fresh specimens, and 
I cannot but expect that some very important modifications, 
in accepted conclusions, may result from a renewed investi- 
gation of the anatomy of that animal carried out upon freshly 
killed individuals. Nor has the nervous system of the adult 
Scorpion been studied by the aid of the microscope, in regard 
to which deficiency we are in the same difficulty so far as 
