PROGKESS OF MICROSCOPICAL SCIENCE. 175 



numerous of which are thick circular disks, varying in diameter from 

 ■JtVo ^° 2 o \) o °^ an i ncn j an d iu these, and these only, the pink 

 colour resides (Fig. 7). These pink corpuscles consist of a clear 

 homogeneous substance, of high refringent power, in which are scat- 

 tered three or four bright granules and a small nucleus, which is 

 rendered obvious by the action of acetic acid. Eosaniline stains this 

 nucleus, but does not usually give any other maculae, such as are to 

 be observed when it is added to Haemoglobin-containing corpuscles.* 

 Dr. Alexander Brandt, in a recent memoir, very rightly insists on 

 the similarity between these pink corpuscles of Sipunculus and the 

 red corpuscles of the blood of Vertebrata : they are something quite 

 distinct from the amoeboid corpuscles found in the fluid corresponding 

 to blood in nearly all Invertebrata, and are to be compared to the 

 red corpuscles of Glycera, Solen, and Vertebrates. The amoeboid 

 corpuscles are otherwise represented in the perivisceral fluid of Sipun- 

 culus by numerous active amoeboid cells. Dr. Brandt, naturally 

 enough, regarded the pink colour of these corpuscles as favouring 

 their assimilation to vertebrate red corpuscles. The colour en masse 

 is, however, obviously different from that of dilute Haemoglobin ; and 

 I was not therefore surprised to find that it did not give the absorp- 

 tion-spectrum of that body. This pink colouring-matter is soluble 

 in water. When a little fresh water is added to some of the perivis- 

 ceral fluid in a tube, it takes up all the colour, whilst the corpuscles 

 sink in a colourless condition to the bottom. No detached bands of 

 absorption of any kind were given by the colouring-matter thus ob- 

 tained ; a slight acidulation with acetic acid was sufficient to destroy 

 the colour. Ammonia had the same action, also ether and alcohol. 



" Though this pink substance is thus devoid of the spectral pro- 

 perties which characterize Haemoglobin and Chlorocruorin, it does 

 not seem improbable that it is a body analogous to them in other pro- 

 perties, since the corpuscles in which it resides can only be compared 

 to the respiratory or oxygen-carrying corpuscles occurring in the 

 blood of Vertebrates and the four Invertebrates noticed in this paper. 

 Moreover, this pink colouring-matter occurs in other parts of the 

 organism of Sipunculus, namely, diffused in the substance of a remark- 

 able tissue which runs along the wall of the intestine, forming a red 

 streak, which has sometimes been taken for a blood-vessel, and also in 

 the peculiar cellular tissue which surrounds the true nerve-tissue of 

 the nerve-chord. 



" The occurrence of colourless corpuscles in Leptoceplialus iden- 

 tical in form and character with the Haemoglobin-bearing corpuscles 

 of the blood of other fish, and the apparently capricious distribution 

 of Haemoglobin among Invertebrata, together with the existence of 

 the green oxygen-carrier Chlorocruorin and the pink colouring-matter 

 of the corpuscles of Sipunculus nudus, suggest the hypothesis of the 

 existence of various bodies not necessarily red, possibly colourless, 

 which act the same physiological part in relation to oxygen as does 

 Haemoglobin." 



* On one occasion out of many I obtained an appearance of the kind ; and 

 hence further observation on this point is necessary. 



