330 H. H. NEWMAN. 



They consist first of a core of horny material or sclerified connec- 

 tive tissue (see Text Plate IV., Fig. 3), that arises like a sharp 

 spike from the free growing edge of the scale. This skeletal sup- 

 port is represented in black in the drawing although in life it is 

 nearly transparent. Various stages in the development of the 

 spikes may be seen both in the detail and in the general drawings. 

 They first appear as slight outwardly directed folds of the edge of 

 the growing region of the scale, and gradually assume the spike- 

 like form. Outside of this horny support there is a fairly thick 

 layer of dermis, represented in the detail drawing in stippling. 

 The histological characters of this layer I have been unable to 

 make out in the formalin preserved specimens that have been 

 my only resource in the present paper. Outside of the dermis 

 there is a thin layer of epidermis that is often found worn off at 

 the tips of the papillae, allowing the horny spike to protrude. 



The contact organs do not lie flat against the body of the fish, 

 but stand out at an angle of about thirty degrees, so that they 

 can readily be seen in profile with the naked eye. This attitude 

 is decidedly advantageous for giving a rough surface or for a 

 sensory function. Probably the former function is the principal 

 one, although I am not sure that the latter function is not sub- 

 served. If the contact organs should prove to be sensory we can 

 understand how their stimulation by the vibration of the female 

 during the spawning act might account for the extrusion of sperm 

 on the part of the male. These points have not been made out 

 on account of the lack of histologically fixed material, but a 

 study of the histology and function of these organs will furnish 

 material for a more special paper. 



It should be stated that the contact organs are possibly related 

 to the so-called " pearl organs " found in other species of fish. 

 Their structure, however, is entirely different in that they are 

 chiefly dermal in origin and possess the horny spike-like support, 

 while pearl organs are little more than epidermal callouses. 



The resemblance of the contact organs to the teeth on the 

 margin of ctenoid scales will probably strike the reader. s lt has 

 occurred to me that here we have the origin of the ctenoid type 

 of scale. Ctenoid scales are found on the most highly specialized 

 of our Teleosts but are described as being absent in more primi- 



