EXTRACTS AND ABSTRACTS FROM FOREIGN JOURNALS. 123 



posed plates ; he asserts, on the contrary, that they are formed of juxta- 

 posed cellules. He endeavours to show it in the scales of Locha ; and 

 yet, in the same fish, I have succeeded in separating the plates, as they 

 grow one upon the other ; and in numerous transverse sections of dif- 

 ferent scales, I have seen, with a power of 250 diameters, the super- 

 position of these plates throughout the whole thickness of the scales ; 

 I have even published a figure of a similar section of the scale of Salmo 

 Trutta, in my Histoire Naturelle des poissons d'eau douce. 



Mandl further affirms, that the diverging traces on the surface of 

 the scales, which I have described as furrows, are true canals. I can 

 scarcely imagine that Mandl has mistaken the middle tubes of the scales 

 of the lateral line (which ramify occasionally at their posterior extre- 

 mity) with the furrows of their surface ; this would be imputing to him 

 too gross an error ; nevertheless, I cannot see (entrevis) any other ex- 

 planation to that which he advances ; but that which I can positively 

 affirm is, other scales never have canals in their surface, but furrows, 

 compressed from above, which are prolonged to the margin of the supe- 

 rior layer of growth to the edge of the next inferior layer, as is 

 evidently seen in all transverse sections that can be made in any scale 

 offering similar traces. 



Mandl is of opinion, that the toothings on the posterior border of 

 pectinated scales are not notches of the borders of the plates, but true 

 teeth, having a root enveloped in a sac. It is quite sufficient to examine 

 the scales of Sciena, which Mandl cites as an example, in adjusting suc- 

 cessively the scale by the focus of the microscope, to be convinced that 

 all this apparent dental apparatus depends on optical illusions, resulting 

 from the difference of thickness of these dentations at their base and at 

 their point ; and that in truth, the points which tooth the posterior 

 border of the scales of fish, which I call Ctenoidce, are simply the result 

 of notches, more or less deep at the border, and not detached 

 teeth. 



Lastly, Mandl appears to be unacquainted with the existence of ena- 

 melled scales, which differ materially in their structure from those of 

 ordinary fish, and are found in an order, of which the greater num- 

 ber of species are extinct, and to which I have given the name of 

 Garoidse. To these, and other remarks, M. Agassiz concludes, from 

 his new observations, that the description he has given on a former occa- 

 sion is exact, and that the manner in which M. Mandl examined the same f 

 is erroneous in every respect. 



To this Mandl replies in a succeeding Memoir, that : 1 . The parts 

 of the scales which I call teeth, are not, as M. Agassiz observes, the 

 result of an optical illusion ; I can show their existence to the Commis- 

 sion. 2. The canals, of which I have spoken assuming different forms, 

 do not exist, according to M. Agassiz : the Commission may convince 

 themselves that they really do exist. 3. I have nowhere stated the 

 opinion attributed to me by M. Agassiz, that the scales are formed of 

 juxtaposed cellules ; I have, on the contrary, shown the presence of two 

 different lamella; I speak, as may be seen in the analysis of my 

 memoir inserted in the Comptes Rendus of the sitting of the 24th June, 

 1839, of superposed lamella in an inferior fibrous layer, and of cellules 



