On certain features of the lateral canals and cranial bones of Polyodon folium. 663 



ion (4), homologous with the terminal buds of teleosts and not with 

 organs related to the lateral sensory system i). 



1) As this is going through the press I have received No. 10/11, V. 21 

 of the Anatomischer Anzeiger in which J. B. Johnston publishes an 

 article entitled, "The Homology of the Selachian Ampullae. A note on 

 Allis' recent paper on Mustelus laevis." In this article, Johnston says: 

 "Mr. Allis makes an argument to show that the nerve sacs of ganoids 

 and the ampullae of selachians are the homologues of the end buds of 

 teleosts, rather than of the lateral or pit-organs. This argument appears 

 to me wholly unsound and likely to lead to further difficulties in a 

 matter which the work of several authors during the last three years 

 has just redeemed from great and needless confusion." 



If this prove true no one will regret it more than myself, but I 

 can not see, as j^et, that Johnston brings forward anything whatever 

 to disprove my position excepting certain general assertions that are 

 certainl}^ not substantiated either by adequate reference or by his own 

 personal investigations. That end buds are all innervated by fibres 

 that "find their central endings in the lobus vagi"; that all other forms 

 of cutaneous sense organs are innervated b}^ fibres that "have their 

 central ending in the nucleus funiculi, tuberculum acusticum, or the 

 cerebellum'" ; that the respective centers for the lateral line and end 

 bud fibres are so separate and stable "that it is utterly impossible for 

 libres or centers to 'undergo modification' of any sort such as I under- 

 stand Allis to mean''; that, "It is impossible that these organs [end 

 buds and lateral line or pit organs] should ever resemble one another 

 in any other than a superficial way"; and that end buds are organs 

 "with visceral function (e. g. taste)", while all other surface sense organs 

 are organs "with a somatic function (e. g. touch &c)", are certainly nothing 

 %ore nor less than deductions from the theory he seeks to establish 

 in his several works instead of established facts on which to base that 

 theory. Of exactly similar character was also his earlier statement, 

 since somewhat qualified, that end buds are all of endodermal origin. 

 His observation on the feeding habits of Aclpenser, made and recounted 

 in order to substantiate his assertion that endbuds are organs of taste 

 and not of touch, is wholly inadequate; for if two or more blind and 

 hungry men were to be put before a table on which they were led to 

 believe that there were articles of food, they would most certainly pass 

 their fingers rapidly over the forks, knives, spoons and plates and close 

 with avidity on an apple, mutton-chop, or other well known article of 

 food, exactly as the sturgeon is said to quickly protrude its mouth 

 whenever its barbies "touch an earthworm or other suitable food-body". 

 Turthermore, Merkel, whom Johnston cites as a competent authority 

 on this subject, considered that the sensation of taste was limited to 

 end buds on the tongues of mammals only. 



As to Johnston's strong exception to Wiedersheim's statement that 

 lateral line organs pass through a stage in their development in which 



