Royal Microscopical Society. 203 



cannibals they really are at times — would not lay on tlieir paint to 

 such a degree. That the tissues which go to form the skeleton 

 may be well understood, it is very important that a morphologist 

 should be a good histologist : he not only has to diagnose between 

 tissue and tissue, he has also to depict other structures than the 

 connective- tissue series in their general anatomical relations. Brain, 

 nerves, muscle, glands, skin, mucous membrane — all and every of 

 their various parts have to be seen, pictm'ed, and described in re- 

 lation. The skull, above aU other parts, is the great warehouse 

 and factory where all sorts of materials and all kinds of machinery 

 have to be placed. The skull in its adult form is the most perfect 

 morphological enigma that can be imagined. Luckily the eyes can 

 be gouged out, yet they are fastened to the skull by a pedicel in 

 the sharks and rays ; but the ear-sac is always in the way, now 

 loose, now combined, then loose again : it does what it likes amongst 

 the real cranial structures, and never is at one stay amongst the 

 various tribes of the vertebrata. 



But the nose is the real difficulty and trouble. The ear pos- 

 sesses its own cartilaginous sac, and although it now marries itself 

 to this and then to the other, yet its ways and doings can be found 

 out with patience ; the nasal sacs have nothing to begin with but 

 membrane, and they borrow this and use that ; creeping along one 

 part and burrowing into another, so that their very earliest infancy 

 must be known if any account of them is to be given. Thus the 

 skull itself is largely made up of parts having a diverse origin. 

 Essentially, in its first membranous condition, it is a " bleb " blown 

 on to the end of the spinal canal to hold the httle sacs that grow 

 out of the front end of the cerebro-spinal axis. 



The vesicles of the brain are superadded to the spinal cord, and 

 they have to be lodged in a cavity that grows with their growth 

 and strengthens with their strength. But the upper part of the 

 axis of the vertebrate animal, after subdividing to form the ver- 

 tebrae, has only an unused piece left, reaching as far as to the 

 pituitary body : about the posterior third of the skull is thus related 

 to the vertebrae, but as an unsegmented piece. From the vertebras 

 rays grow downwards tending to enclose aU the thoracico- abdominal 

 viscera ; but under the head free bars are found belonging to quite 

 another category of skeletal organs. These carry the gills behind, 

 and become the face, palate, and forepart of the skull, anteriorly. 

 The foremost pair of these bars are called the " trabeculas," or 

 rafters ; they lie above and in front of the mouth, and coalescing 

 after a time with the vertebral remnant at the back of the head, 

 form much of the skull. 



The second pair form the arch of the lower jaw, and, sending a 

 secondary bar across to the trabeculas, form what is called the 

 " ptery go-palatine " arcade. The third [)air of bars are related to the 



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