ANATOMY AND LIFE HISTORY OF MOLLUSCA. 123 



be the suitable agent employed. The Vertebrata and Annelida 

 possess a blood containing haemoglobin, being of greater activity 

 than the Mollusca, which do not possess such blood as a rule. 

 The actively burrowing Solen legumen alone amongst Lamelli- 

 branchiate Mollusks and only Planorbis amongst Gastropods, 

 respiring the air of stagnant marshes, possess blood containing 

 haemoglobin. In the former the activity, in the latter the 

 deficiency of respirable gases are correlated with the exceptional 

 development of haemoglobin. But we cannot as yet offer an 

 explanation for the absence of haemoglobin from the closely-allied 

 species of Solen, and from the Lymncei which accompany Planorbis.. 



Haemoglobin-bearing corpuscles are, according to the same 

 author, of a peculiar character. When haemoglobin is absent, other 

 things remaining the same (as with the blood of Solen ensis, L.), 

 the peculiar corpuscles are absent also. Such things as colorless 

 corpuscles representative of haemoglobin do however appear to 

 exist in the case of the fish Leptocephalns. In connection with 

 the relation of the colorless corpuscles of vertebrate blood to the 

 red corpuscles, and of the corpuscles of the vascular fluids of 

 Invertebrata to one another and to those of Vertebrates, these 

 facts seem to be important ; the colorless corpuscles in one case 

 are only comparable to the colorless in another ; the reel corpuscles 

 are something apart, which may or may not be superadded. 



Dr. Lankester mentions in another place a species of Area, in 

 the blood of which he detected haemoglobin, and which I believe 

 is of a red color. Without being able to say anything as to the 

 occurrence of haemoglobin, I wish to record here that one species, 

 very common in all muddy places on the extra-tropical Australian 

 coast, and particularly so in Port Jackson (Area trapezia, Desh., 

 = A. lobata, Reeve), has red blood, very like in color and 

 appearance to the blood of a vertebrate animal. When examined 

 under the microscope, the red color is seen to be due to corpuscles, 

 with a nucleus exactly like human blood, except that the corpuscles 

 appeared to me to be not quite so proportionately numerous as in 

 the human fluid. There was an absence also of any of the 

 amoeboid movements, so well known and so often described. The 

 size also appeared to correspond with that of the human corpuscle 

 with a scarcity of colorless discs. 



When a living specimen of Area trapezia is opened, the injury 

 to the tissues, as in the case of the oyster, causes the blood to 

 flow freely, and the heart may be seen to be pulsating at the rate 

 of about 15 or less pulsations per minute. On these occasions it 

 appears like a little vesicle fully injected, and can be easily studied 

 in that position. As already stated, if a piece of the gill is now 

 removed and placed under the microscope, innumerable crowds of 



