196 MR. F. J. COLE O'S THE STRUCTURE AND MORPHOLOGY OF 



which keeps a coustant position in prejoarations because it is retained by the numerous 

 sensory hairs " (p. 81). Here Cunningliam has overlooked the gland cells at the base of 

 the sense organ, which are doubtless responsible for the secretion of the cvipula. There is 

 therefore no necessity to suppose that it is secreted by sensory cells. Fritsch (1890, 77) 

 was again unable to find a cupula in the Torpedoes, but afte r careful investigation 

 admitted that the lateral sense organs agreed very closely in their minute histology with 

 those of the auditory organ. 



In 1892 Ayers published his elaborate and important memoir on the morphology of 

 the vertebrate ear (7). In this work he endeavours to show that the cupuloe terminates 

 of the lateral and auditory sense organs are " artifacts produced in the main from the 

 auditory hairs of the sensory cells " (p. 314). He says (p. 163) : — " Now, while there is 

 no question that some mucus is present in all cases (all in which exact analyses have yet 

 been made), there is no evidence to show that in a state of nature it exists as a dome- 

 shaped mass covering the sense organ. On the other hand, it is clearly proven that the 

 most typical cupulae yet studied are products of the action of reagents, and that so far as 

 fibrous structures in the channels occupied by sense organs (whether car organs or those 

 of the lateral line system) are concerned, they have in every thoroughly studied case 

 shown themselves to be hairs more or less unchanged." I have previously referred to 

 the existence of cupuloe over the lateral sense organs as evidence that the latter and the 

 auditory organ are genetically related. Whether the cupulye are artifacts or not is a 

 question that does not affect this argument, since the conditions producing the artifact 

 must be the same in both cases, and the ai'tifact therefore open to be used in argument 

 as denoting equally important and similar conditions in both systems of sense organs. The 

 following quotations from Ayers' valuable monograph briefly summarise his line of 

 argument : — " The whole process of the formation of this [auditory] cup is an exact 

 repetition of the formation of a canal organ and its canal as seen in Amia, or tlie 

 formation of an ampulla and its canal in the Salmon " (p. 175). "There could not be a 

 more complete agreement between two developmental processes, occurring in diff^erent 

 animals, than there is between the formation of the canals on the surface of the body in 

 Amia and the formation of the canals of the internal ear in the Herring and Salmon, as 

 given by Von ISoorden. Of the correctness of the account for the latter I am certain, for 

 I have observed the same process both in the whole embryo and serial sections. From 

 uur present knoAvledge of the development of tlie labyrinth in the bony fishes we have 

 only agreement with the type of growth of the surface organs " (p. 181). " The so-called 

 semicircular canals develop as more or less curved structures, because they are formed 

 out of a portion of the external surface of the body, which has been enclosed within the 

 head. Since on the sxu-face of the body, in the typical and usual process of develojiment, 

 the canals always open at both ends on the surface, so inside the auditory vesicle they 

 open at both ends " (p. 222). " It is proven that there is no essential difference between 

 the sense organs of the internal ear of the vertebrate group and the superficial sense 

 organs of the Ichthyopsida as they exist in the surface canals of these forms. Both 

 consist of canals containing sense organs lying below the surface of the body, and they 

 may (as in ordinary canals and the ear in some Elasmobranchs) or they may not (as in 



