2IO 



THE ORIGIN OF VERTEBRATES 



This, in my opinion, is the last remnant of one of the old liver-ducts 

 which extended from the original stomach and intestine into the 

 cephalic liver-mass. This glandular-looking material is shown 

 surrounding the pineal eye and its nerve, in Fig. 31, also in 

 Fig. 22, and separately in Fig. 92. It is composed of large cells, 

 with a badly staining nucleus, closely packed together with lines 

 of pigment here and there between the cells ; this pigment is 

 especially congregated at the spot where the so-called liver-duct 

 loses itself in this tissue. The protoplasm in these large cells does 

 not stain well, and with osmic acid gives no sign of fat, so that 



Ahlborn's description of this tissue as a 

 peculiar arachnoideal fat -tissue is not 

 true ; peculiar it certainly is, but fatty 

 it is not. 



/ : .. '"l^^V ^ n * s ki ssue nas Deen largely de- 



: 7\ scribed as a peculiar kind of connective 



tissue, which is there as packing mate- 

 rial, for the purpose of steadying a brain 

 too small for its case. On the face of 

 it such an explanation is unscientific ; 

 certainly for all those who really believe 

 in evolution, it is out of the question 

 to suppose that a brain-case has been 

 laid down in the first instance too large for the brain, in order 

 to provide room for a subsequent increase of brain ; just as it is 

 out of the question to suppose that the nervous system was laid 

 down originally as an epithelial tube in order to provide for the 

 further development of the nervous system by the conversion of 

 more and more of that tube into nervous matter. Yet this latter 

 proposition has been seriously put forward by professed believers in 

 evolution and in natural selection. 



This tissue bears no resemblance whatever to any form of con- 

 nective tissue, either fatty or otherwise. By every test this tissue 

 tells as plainly as possible that it is a vestige of some former 

 organ, presumably glandular, which existed in that position ; that 

 it is not there as packing material because the brain happened 

 to be too small for its case, but that, on the contrary, the brain 

 is too small for its case, because the case, when it was formed, 

 included this organ as well as the brain ; in other words, this tissue 



Fig. 92. — Drawing of the 

 Tissue which surrounds 

 the Brain op Ammocoetes. 



