124 ANATOMY AND LIFE HISTORY OF MOLLUSCA. 



red discs may be seen coursing down the channels around the 

 filaments. 



The fact of another species of Area in the Southern Hemisphere 

 having red blood is one of considerable interest, and I trust it 

 will soon be ascertained whether it contains haemoglobin, of which 

 there can be but little reasonable doubt. The habits of the 

 animal are such as to require some highly oxidizing element. 

 Like Solen ensis in Britain, it buries itself deeply in the sandy 

 mud and silt when the tide recedes, and comes to the surface 

 when the water is in. The mud in which it lies buried is so finely 

 lsevigated that it can generally sink to considerable depths, and 

 the surrounding ooze must penetrate into every crack and crevice 

 and exclude every particle of oxygen. Under these circumstances 

 it would need, it seems to me, all that haemoglobin could do for it. 

 The habits of the Solens are similar, except perhaps that in 

 burying themselves they seem to prefer sand to mud. Often 

 when a lad I have captured numbers of Solens by searching for 

 their place of interment, indicated on the surface by a small 

 perforation like a keyhole. Putting a little salt on the hole, and 

 then a little water, generally brought the animal to the surface. 

 It used to be said that it came up because the salt made it think 

 the tide was rising, but probably as much was due to an 

 unexpected shower bath of strong brine. 



There are two species of Solen in Sydney Harbour, differing 

 but little from each other ■ but their blood is red like that of 

 Solen ensis in Britain. It may be observed that burrowing alone 

 to great depths is not a habit which necessarily indicates red 

 blood amongst Mollusca. JVatica, many of the species of Venus, 

 Cardium, Mactra, Donax, and many others, are all burrowers, 

 and none of them, as far as I know, have blood different from 

 the usual Molluscan character. 



I have not had any opportunity as yet for the examination of 

 the blood of any of our species of Planorbis. The red color of 

 its blood has been asserted, contradicted, and re-asserted many 

 times. In Prof. Tate's admirable and painstaking little book on 

 the " Land and Freshwater Mollusks of Great Britain," (London, 

 Hardwick, 1866,) he says, "The species that compose this genus 

 are numerous, inhabit slow running streams, ponds and ditches, 

 feeding on the aquatic plants, and are very sluggish in their 

 movements. A peculiarity possessed by all the genus, may be 

 readily observed by irritating the animal of P. corneus or P. 

 marginatus, when a purplish liquid is emitted, which is not the 

 blood, for the circulating fluid is colorless," p. 210. 



I believe that the one Tasmanian species, and one if not more 

 of the Australian species have colored blood, but I have not 

 subjected the fluid of any of them to microscopic examination. 



