7 6o THE POPULAR SCIENCE MONTHLY. 



Not the least interesting feature of this localized mass of nervous 

 matter is the fact that it exhibits the same arrangement of gray and 

 white nerve-matter that is seen in the highest brains. An outer gray 

 and an inner white layer are discernible in the nerve-ganglia of cepha- 

 lopods, as in the cerebrum of man ; and, as in the highest animals, 

 the cuttle-fish gray matter is found to consist of nerve-cells, while 

 the white matter is chiefly composed of nerve-fibers. Thus the laws 

 of developmental progress affect the microscopic and intimate struct- 

 ure of the living form as well as the more obvious details of structure. 

 From the main nerve-mass of the cuttle-fishes nerves arise to supply 

 the body at large. Nerves of special sense supply eyes, ears, and 

 olfactory organs ; while the viscera and the " mantle " or general 

 body-covering are also well provided with the means of innervation. 



Cuttle-fish existence possesses, in all probability, the five "gate- 

 ways of knowledge," through which the impressions of the outer 

 world are received, and by which these impressions are modified and 

 transmitted to the brain-masses as sensations of sight, hearing, smell, 

 touch, and taste. There is little need to draw upon hypothesis in the 

 assumption that the arms or tentacles are efficient organs of touch in 

 Cephalopoda, or that the structures of the mouth may subserve taste, 

 in so far as the latter sense may be required to satisfy the demands 

 of cuttle-fish existence. An organ of smell is definitely situated behind 

 or above the eyes. There two small projections, or, as frequently, two 

 minute pits or depressions, occur. These pits are ciliated, and be- 

 tween the cilia " olfactory cells " are situated. These cells, in turn, 

 represent the similar structures which occur in higher animals, and 

 which, in man himself, form the characteristic terminations to his 

 olfactory nerves. That the cuttle-fishes can literally scent their prey 

 from afar off is an idea confirmed by the facts of their every-day 

 life. 



The " ears " of the cuttle-fishes present us with two sacs named 

 " auditory sacs " which may, as in the nautilus, either be attached 

 to the chief nerve-mass itself, or, as in the two-gilled cuttles, be 

 lodged in special cavities in the gristly "skull." A cuttle-fish "ear" 

 is essentially a sac or bag, called an " otocyst," containing either one 

 or many "otoliths" or "ear-stones," suspended in a watery fluid. 

 This, indeed, is the primitive type of " ear " we may find even in the 

 MedusidcB or " jelly-fishes " themselves. The ear-sacs of many cuttle- 

 fishes open on the external surface of the body by two fine canals, 

 named " Kolliker's ducts," after their distinguished discoverer. Occa- 

 sionally these ducts end blindly, and do not open on the body surface. 

 These facts lend additional support to the opinion that in the ear of 

 the cuttle-fish we find primitive structures proper to the ears of verte- 

 brates, the minute canals of Kolliker corresponding with the recessus 

 vestibuli of the vertebrate organ of hearing. Once again, therefore, 

 we find the progressive development of cephalopods and vertebrates 



