SKELETO-TEOPHIO TISSUES AND OOXAL QLANDS. 189 



Mygale is more strongly fissured than is that of either Limulus 

 or Scorpio, and concurrently we find larger groups of cells 

 gathered together than in the two other forms (PI. VII, 

 fig. 4). Cell-protoplasm, nuclei and matrix present the same 

 appearance and the same staining reaction as in Limulus and 

 Scorpions. 



Over and above this the peripheral regions of the entosternite 

 of Mygale present a feature which I have not observed in either 

 Limulus or Scorpio, and which is not shown in its more central 

 region, from which the specimen given in Pi. VII, fig. 4, is 

 taken. In a large fissure here and there one observes in the 

 peripheral outgrowths of the entosternite, besides numerous 

 nucleated cells, a highly refringent substance of a very pale 

 brownish tint, quite homogeneous and transparent, except for 

 the fact that it is arranged in spheroidal masses more or less 

 closely pressed against one another, the space left between such 

 spheroids and the wall of the fissure being occupied by the cells 

 elsewhere characteristic of the fibro-massive tissue. I do not 

 know the chemical nature of this substance ; its relation to 

 solvents shows that it is not fat, and by its homogeneity and 

 refringency and colour it differs widely from the matrix of the 

 fibro-massive tissue. It may be spoken of as '^colloid 

 substance" (see PL XII, fig. 3, col). Its presence in the nests 

 of cells scattered through the fibroid matrix is clearly due to 

 the activity of those cells, and may be compared to the presence 

 of fat in cartilage cells. But it is to be noted that this colloid 

 substance is not like fat, an entoplastic product; it does not lie 

 within the protoplasm of the cells, but is ectoplastic, that is, 

 around and outside of them, just as is the common fibroid 

 matrix, in the formation of which some of these same cells must 

 be active. 



The production of this colloid may, perhaps, be regarded as a 

 functional degeneration or change of chemical activity of the 

 outlying regions of the fibro-massive tissue of the entosternite, 

 in which alone it occurs. It occurs, however, in anotlier oi'gaa 

 in a very marked form without any relation to fibroid skeletal 

 tisisue — namelv as a sort of skeleton or framework to the 



