616 PROFESSOR E, RAY LANKESTER. 
absence of any adequate investigation of fresh specimens of 
Scorpio, how far the resemblance may go; but, depending 
upon the careful dissectious by Newport of spirit specimens 
(and discarding those of Dufour which are very incomplete), 
we are able to point to very close agreements. 
In Limulus a more complete vascular system has been 
demonstrated than in any other Arthropod, and Scorpio 
comes nearest to it in this respect of all members of the 
group. The arterial channels do not end in wide spaces 
bounded by the connective (vasifactive) tissue which clothes 
muscles and viscera, but the connective tissue here, as in 
other animals in which fine vessels are developed for the 
passage of the blood, forms in most regions of the body a 
series of canals, which constitute a capillary system and lead 
into definitely constituted veins. 
It is worthy of remark by the way that canalisation of the 
connective tissue is the same phenomenon and due to the 
same processes of growth in all Arthropoda, whether the 
canals so formed are connected with the atmospheric air by 
stigmata or are filled by the blood fluid of the primitive 
ceelomic cavity. 
It does not fall within the scope of this memoir to give a 
detailed account of the vascular system of Limulus; for that 
the reader is referred to the memoir of M. Milne-Edwards. 
I shall content myself with drawing attention to the agree- 
ment between Scorpio and Limulus in respect of—(1) the 
existence of capillaries and veins; (2) of the well-developed 
vessels conveying blood to the limbs and viscera, and more 
especially in respect of the great spinal artery and its mode 
of origin ; (3) of the intimate association of the arteries and 
nerves ; (4) of the details of the structure of the heart. 
The memoir by George Newport, in the ‘ Philosophical 
Transactions’ for 1843, and that by M. Alphonse Milne- 
Edwards, in the ‘ Annales des Sciences Naturelles’ of 1873, 
contain the exposition of the facts in detail relatively respec- 
tively to the Scorpion and the King Crab. Of the latter 
animal, M. Milne-Edwards says: “The venous blood, in 
place of being distributed in interorganic lacune, as in the 
Crustacea, is in a considerable portion of its course enclosed 
in special vessels whose walls are perfectly distinct from the 
adjacent organs ; they often take their origin in ramifications 
of a remarkable delicacy and lead into reservoirs which are 
for the most part definitely circumscribed. The nutrient 
liquid passes from these reservoirs into the branchie, and 
after having traversed these respiratory organs, passes by a 
system of branchio-cardiac canals into a pericardial chamber, 
