84 WILLIAM PATTEN. 



Moreover the gustatory cells in Limulus, and the various 

 sense buds arising from the supra-branchial sense organs in 

 Vertebrates, are arranged in straight lines, a condition, so 

 far as I know, found in Arachnids and Vertebrates only. Now 

 whether this arrangement in lines is due to the method of 

 growth or to a physiological necessity is doubtful. Neverthe- 

 less this condition may be taken as evidence of genetic 

 relationship between the forms in which it occurs. And 

 finally, this being what I regard as of most importance, we see 

 that in Limulus the olfactory organ^ besides its other resem- 

 blances to the Vertebrate organ, contains the same kind of 

 buds as those in the segmental gustatary organs. As is well 

 known, the same thing occurs in Vertebrates. Now we 

 might suppose, as has been done in Vertebrates, that the 

 olfactory organ is serially homologous with the mandibular 

 gustatory organs. But the whole development of the organ 

 and its nerves shows that in Limulus this view cannot be 

 entertained for a moment. The olfactory organ in Limulus 

 is obviously a new growth on an old foundation. The latter, 

 it is true, is a segmental sense organ, but it belongs to the 

 series including the ocelli and compound eyes, not to that of 

 the thoracic appendages. 



The same interpretation applies, I believe, to the olfactory 

 organ of Vertebrates, as Limulus appears to be less intelligent 

 than animals like Lobsters, Scorpions, and Spiders, in which 

 there are no cerebral hemispheres or any organ that may be 

 regarded as a psychic centre. It is very surprising that it 

 should possess gigantic cerebral hemispheres, and in shape, 

 structure, and development like those of Vertebrates. This 

 may be a coincidence. But can it be a coincidence that in 

 both Limulus and Vertebrates these cerebral hemispheres are 

 connected with only one pair of nerves ? Is it a coincidence 

 that these nerves arise from the same brain region, have the same 

 lobes, and supply sense organs that show striking similarities 

 in position, structure, development, and function ? It cannot 

 be. Not one of these characters obtains elsewhere, and, in my 

 judgment, it is impossible that all of them should occur in 



