636 
DR. T. WILLIAMS ON THE BLOOD-PROPER AND 
history of the fluids, the articulated classes come here into contact with the annulose 
series. In the embryonic condition of the Myriapod and the Insect, the circulating 
fluids present all the essential characters of the chylaqueous system, as already 
described in the economy of the Annelid. It is a fluid surrounding the rudimentary 
intestine, and moving to and fro in a spacious chamber, its movements being deter- 
mined by no other power than the muscular contractions of the intestine on the one 
side, and the integuments on the other, by which the containing cavity is bounded. 
It is a veritable chylaqueous system. The dorsal vessel is yet Mwformed, the cor- 
puscles of the fluid, scanty in those of the larvse of many species, are temporary 
provisions, destined soon to be replaced by those permanent elements by which the 
blood of the perfect animal is afterwards to be distinguished. 
When the embryo of the articulated animal first emerges from the ovum, it is 
virtually an Annelid in outward form and internal structure. The system of the 
nutrient fluids, and the fluids themselves, fall obviously under the character of the 
chylaqueous type. The perfect absence of independent conduits circumscribing a 
highly organized fluid, reduces the larva of the Insect to the low standard of the em- 
bryo Annelid. Here then is an unequivocal demonstration of the proposition that 
the articulated series are directly continuous with the annulose through the medium 
of the fluids ; that the chylaqueous system is traceable from the latter into the former ; 
that which is persistent in the Annelid is temporary only in the articulated animal. 
These generalizations are founded upon faithfully observed facts, the value of which 
in philosophical zoology cannot be exaggerated. In relation to the nutritive fluids 
of the articulated series, it is proposed now that we proceed to the establishment of 
the following propositions : — 1st, that in the embryonic condition of the Myriapoda, 
Insecta, Arachnida and Crustacea, the fluids, in composition and plan of circulation, 
fall under the designation of the chylaqueous system which persistently prevails in 
all classes below the Articulata ; 2nd, that although in the articulated animal the 
chylaqueous fluid and the blood-proper have in no instance a contemporaneous 
existence in the same individual, yet that these two orders of fluid are marked by 
such strikingly diverse physical characters that their distinctness and independence 
cannot be doubted ; 3rd, that the corpuscles contained in the embryonic or chyl- 
aqueous fluid of the Articulata present varieties in form, structure and size, far 
different from and more numerous than those which occur in the corpuscles of the 
true-blood of the adult animals ; 4th, that throughout all articulated animals, from 
the Myriapod to the highest Crustacean, the mature corpuscles of the true-blood 
conform unequivocally to one fundamental type of structure and figure, a novel de- 
monstration of a new order of zoological affinities ! 
Myriapoda. — It was observed by Mr. Newport that in the larva of lulus the fluid 
filling the space around the intestine, for some days before the pulsations of the dorsal 
vessel, became detectable to the eye. The truth of this statement I have repeatedly 
confirmed. The fluid of the visceral cavity in the larvae oscillates to and fro before 
