Report on Zoology. 



135 



is prepared to pass through a process of moulting. He 

 says that just before hatching, the cephalothorax spreads 

 out and the whole animal becomes broad and flat, the ab- 

 domen being a little more than half as wide as the cephalo- 

 thorax, the two eyes, placed well back, and the ocelli on 

 the edge of the cephalothorax, make their appearance. 



It is at this stage more especially that he recognizes the 

 strong structural resemblance to the Trilobites, and also 

 draws some inferences respecting the relations of the Lim- 

 ulus and the extinct animals, concluding that they should 

 be ranked as genera of the same order, and that the habits, 

 history and organization of the one may throw much light 

 upon those of the other. He remarks that the position of 

 the eyes show that trilobites had long and slender optic 

 nerves indicating general similarity in the nervous system 



In connection with Dr. Packhard's remarks regarding 

 the resemblance of these ancient organisms to existing eyes, 

 it is interesting to recall the eloquent words of the eminent 

 geologist, Dr. Buckland, who was first to call attention to 

 this point, many years ago, and who showed that not only 

 were the organs of vision in the tribolites and limuli simi- 

 lar, but that the condition of the sea and atmosphere 

 was not unlike that at the present time. 



" Thus," says Dr. Buckland, " we find among the earliest 

 organic remains, an optical instrument of the most curious 

 construction, adapted to produce vision of a peculiar kind, 

 in the then existing representatives of one great class in the 

 articulated division of the animal kingdom. We do not 

 find this instrument passing onwards, as it were, passing 

 through a series of experimental changes from more simple 

 into more complex forms ; it was created at the very first, in 

 the fullness of perfect adaptation to the uses and condition 

 of the class of creatures to which this kind of eye has ever 

 been, and is still, appropriate." 



