CHYLAQUEOUS FLUID OF INVERTEBRATE ANIMALS. 
597 
definable walls ; and that in the Gasteropods and Cephalopods the visceral or peri- 
toneal cavity forms a part of the circle of the blood’s movement*.” 
The observations of Milne-Edwards have been repeated by Valenciennes-!', by 
Professor Owen:|; on the Brachiopods, by E. Blanchard among the Entozoa§, by 
Quatrefages and others. It has been doubted however by Hancock and Embleton 
whether the views of Milne-Edwards with reference to the laciinose character of the 
peripheral segment of the circulating system in Mollusca, express the true type of 
the circulation in the Nudibranchia. 
While acknowledging the extreme interest of the discoveries accomplished by the 
latter distinguished men, they will be found in every instance to be limited merely 
to “the system of conduits” through which the blood describes its circulation, 
distinct therefore in object and subject from those inquiries which are specially 
addressed to a consideration of the characters and relations of the nutrient fluids 
themselves, and which it is the purport of this memoir to record. 
The Mood itself was, made the subject of more special remark by Sir E. Home]], 
who states that the blood of the Teredines is red, and that of the Planorbis purple. 
Milne-Edwards says that in the vicinity of Palermo he discovered an Ascidian with 
red bloody. The blood in Lamellibranchiate Mollusks has been made the subject 
of observation by Mr. Garner**, with whose results, those stated in this paper will 
be found little to coincide. 
Lister proved that the blood of the Snail was coagulable'!''|', and that that of the 
Ascidise contained globules. The conclusions of Lister were confirmed by Prevost and 
Dumas:};;J;, by whom it was supposed to have been shown that the globules in the blood 
of the Snail have a diameter one-third greater than those of man and quadrupeds. 
PoLi §§ has observed, “ si tamen in bono microscopio examinetur, id est, syphone 
* “ Chez les Mollusques, de meme que chez les Crustacds, une portion plus ou moins considerable du cercle 
parcouru par le sang en mouvement est toujours constitute par les lacunes ou espaces interorganiques ; jamais 
ce liquide ne se trouve emprisonne, comme on le supposait, dans un systbme clos et complet de vaisseaux a 
parois propres ; quelquefois il n’existe, pour une portion considerable du corps, ni artbres ni veines, d’autres 
fois les eirtbres portent le sang partout ou il y a vie a entretenir, mais il n’y a pas de veines pour assurer le 
retour du fluide nourricier qui s’epanche dans les lacunes comprises entre les diverses parties solides de I’or- 
ganisation ; d’autres fois encore, I’appareil de la circulation se perfectionne davantage, car il existe des veines 
aussi bien que des arteres dans une portion plus ou moins grande du corps ; mais ces veines ne suffisent 
jamais pour compltter le cercle que le fluide nourricier doit parcourir, et la cavite abdominale ou ptritoneale 
joue toujours le role d’un reservoir sanguin aussi bien que d’une chambre viscerale.” — Op. cil. 
f Nouvelles observations sur la constitution de I’appareil circulatoire chez les Mollusques, par Milne- 
Edwards et Valenciennes. — Ihid. p. 307. 
J Lettre sur I’appareil de la circulation chez les Mollusques de la classe des Brachiopodes ; addresse h 
Milne-Edwards par M. R. Owen. 
§ Annales des Sciences Naturelles, 3™' str. tom. iv. || Comparative Anatomy, vol. i. p. 32. 
^ Elem. Zool. p. 18; and Mag. and Ann. Nat. Hist. vol. xv. 69. 
** Charlesworth’s Magazine, Nat. Hist. vol. iii. p. 168. 
ff Philosophical Transactions for 1834, p. 380. U Bostock’s Physiology, vol. ii. p. 200. 
§§ Exert. Anat. de coch. p. 95. 
4 H 2 
