THREAD-CELLS AND KTinKKMIS OF MYXINE. 357 



is the staining fluid which is most useful from its differential 

 colouring of the various structures — there is seen {cf. fig. 1) 

 most externally the epidermis, succeeded by the dermis, 

 which in its turn i*ests on a peculiar subcutaneous connec- 

 tive tissue, much resembling the notochordal variety of that 

 group in its general appearance, and these two latter struc- 

 tures merit a short account. 



The subcutaneous tissue is rather remarkable. In a 

 specimen which has been in spirit below the dermis there is 

 seen an irregular network composed of spherical or hexa- 

 gonal meshes, each mesh being composed of fibrous tissue 

 continuous with and running into the dermis, and holding 

 somewhere in its lumen a granular nucleus with nucleolus, 

 which sometimes takes up a central at other times a parietal 

 position (PI. XXX, fig. 1 c). 



If now a specimen be examined which has not been sub- 

 jected to the action of spirit, but preserved in picric acid, 

 this network is found to be filled with an oily yellow liquid, 

 occupying the spaces in which the fibres and nuclei may be 

 traced as before. 



This tissue is to be regarded as adipose tissue, in which 

 the jnimitive cells, supported in a framework of fibres from 

 the dermis, have by a process of cell secretion become 

 metamorphosed, leaving only the fibrous stroma and nuclei 

 floating in the oil to testify to their former condition. 



The dermis is a structure composed of layers of fibrous 

 tissue, which take up the carmine of the picrocarmine and 

 assume a bright pink colour. Here and there between the 

 laminae may be seen pigmented cells (fig. 1 h). 



The epidermis rests on the dermis (fig. 1 a), and is composed 

 of several layers of cells, among which a difference may at 

 once be recognised by the use of a staining fluid, such as borax 

 carmine, which divides it into two portions, of stained and 

 unstained matter, much in the same way that the epidermis 

 of higher vertebrates is distinguished into the stratum mu- 

 cosum and stratum corneum, the stained portion being com- 

 posed of living protoplasmic cells and the unstained portion 

 of formed cells, whose protoplasm has disappeared in the 

 process of producing the particular body which in the case 

 we are considering is mucus and in the higher vertebrates 

 keratin. 



That the substance is mucus in the case of Myxine is 

 probable from the shape of the cells, which conform in 

 character to the typical mucus or goblet cells found in the 

 alimentary and respiratory tracts. These goblet cells are 

 arranged in series two or three deep. They vary slightly 



