INVEKTEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC. 407 



Any discussion of the mode and significance of the formation of 

 haemoglobin in the mammalian blood ought to take cognizance of the 

 fact that ha;moglobin is formed in the blood of the worms above noted, 

 in insect larvae, Crustacea, and even molluscs ; and further, that whilst 

 it usually occurs difi"used in the plasma of the blood, it does occasion- 

 ally, as in the Chaetopods Glycera and Capitella, the molluscs S'olen 

 legumen and Area sp., &c., take the form of speci.al nucleated cor- 

 puscles differing from and accompanied by the usual amoeboid colour- 

 less corpuscles ; also, it is to be noted that just as fat occurs in other 

 cells than specialized fat-cells, so do we find the muscular tissue of 

 many vertebrates and of some molluscs (buccal mass) impregnated with 

 haemoglobin. And even in one annelid (the sea-mouse Aplirodite), wo 

 have the cells of the nervous tissue so rich in it, that the nerve-cord 

 is of a deep crimson colour.* 



Epithelial Cells.t — Signer Trinchese considers that neither in 

 these nor perhaps in any animal cells does protoplasm exist — in the 

 condition generally described by histologists — dvu-ing life. In other 

 words, the so-called " protoplasm " is the result of profound post- 

 mortem changes, which produce the ground substance, interspersed 

 with gi'anules, which we know under that name. 



When alive, the epithelial cell consists of 



1. A nucleus and nucleolus. 



2. A network of spherical granules, spreading over the body from 

 the nucleus. 



3. Some spheroidal, homogeneous corpuscles, each containing a 

 central granule resembling the nucleolus suspended in the network 

 just mentioned, to be called protomeres. These are probably iden- 

 tical with the "elementary globules" described by Arndt in the 

 ganglion-cells of Vcrtebrata. 



When the cell is treated with y^/„^ per cent, osmic acid, the nucleus 

 and the protomeres assume a transparent gray colour, while the 

 granules, the nucleolus, and the corpuscles of the protomeres become 

 black. 



The reticular intracellular structure first described by Ileitzmann 

 is not, therefore, an artificial product, but exists in the living state ; 

 its existence may be satisfactorily determined in the dorsal papilho 

 of the mollusc Janus cristatus by a high magnifying power. The 

 meshes of the network vary greatly in size in different animals. 



Living Cartilaginous Cells.J — Herr Schleicher's observations 

 follow on those lately pultlished by Pruden, which were thus 

 effected ; in a eurarizod frog the episternal cartilage was dissected 

 out and placed on a glass plate under the Microscope. The cartila- 

 ginous plate thus remained in connection with the blood-vessels, and 

 researches could be carried on in a living tissue. 



In giving an account of his own investigations, Schleicher com- 

 mences by saying that the interior of the nucleus of a living cur- 



• Seo *Proc. Roy. Soc.,' No. 140 (1873). 



t ' Atti R. Accnd. Lincei (Tranannt.V iv. (1880) p. 45. 



: ' Arch. Biol.' (Van lieucdon) i. (1880) p. 65. 



