MORPHOLOGY OF TUB BRAIX IN THE MAMMALIA. 381 



Tarsius, and Uapale, is shown in the accompanying- drawings (fig. o2). In Tarsias and 

 JIapale the swelling exposed is partly and perhaps wholly a true calcar, like that of 

 Cercojnthecus. 



In the hrain of the Apes, as also in Lemurs, tlie walls of the paracalcarine and 

 retrocalcarine sulci do not come into relationship Avith the ventricle. 



If next we practice a corresponding section in the hrain of a Dog (fig. 53), a state of 

 affairs is exposed which is either identical witli (hat of tlic brain in th(? Primates 

 or presents the closest resemblance to it. Immediately to the caudal side; of the 

 liippocampus the neopalliiun behaves in tlie same manner as it does in the brain of 

 Lemurs and Apes ; but tlie deop, oblique sulcus is not usually called " calcarine," but 



Fig. 53. 



calr 



— sc. 



Can is film Uiaris. 

 A section analogous to these represented ia tigs. 50 aud 5L x i*. 



by Krueg's title " splenial." A glance at this figure will at once show that, unless there 

 be some overwhelming argument to the contrary, we must regard this part of the splenial 

 sulcus of the Dog as the representative of the calcarine sulcus of the Primates. It is 

 commonly argued that there can be no calcarine sulcus in the Carnivora because there 

 is no posterior cornu ; Ijut the same writers do not deny the calcarine nature of the 

 analogously-placed furrow in the Lemtirs, even though tliere is no posterior cornu there. 

 We may therefore, at any rate as a working hypothesis, refer to this part of the Dog's 

 splenial sulcus by the name " calcarine." Now the conditions which are found in the 

 Dog also ^n-evail in every Carnivore, without exception. It is therefore very surprising 

 to find Plower speaking of "the absence of anything resembling the calcarine sulcus" 

 in the Cat's brain in the same memoir in which he made the important observation 

 (quoted above) that the existence of a patent posterior cornu is not a necessary condition 

 of the presence of a calcar, and therefore of a calcarine sulcus. Even if the calcarine 

 sulcus should ultimately prove to be not homologous with any part of the splenial 

 furrow, it is clearly erroneous to say that the latter does not " resemble " it. In the 

 case of certain Carnivores, such as the Seals, a definite posterior cornu of the ventricle 

 is found, and in some cases, c. g. Phoca, it reaches large dimensions : in these animals 

 the "splenial bulging" in the lateral ventricle so closely "simulates " the "calcar'' of 

 the Primates that there can be no reasonable doubt as to their identity. This fact was 

 well known early' in the last century, for Serres's observations, that " the hippocampus 

 minor [calcar] has hitherto been observed only in Man," which continue ". . . . I have, 



