248 WHALES 



of cephalization, \vhich is only to be expected from the fact that a thirty- 

 five-ton Sperm Whale has a bigger brain than a 55-ton Blue Whale. 



More recently, Dubois's classification has been challenged by many 

 biologists ^vho have found that, as more material was being investigated, 

 the dividing line between the different stages became increasingly blurred, 

 and that Dubois's formula itself was open to serious criticism. It appeared 

 that not only the ratio of brain-to-body-weight and brain-to-body-surface, 

 but also the ratio of brain-to-brain-stem, and of cerebellum and cerebrum 

 separately to brain-stem, had to be considered. It is particularly Prof. 

 A. Portmann (Basel) and his students who have shown how much more 

 complicated the whole subject is than used to be thought. This became 

 very clear from the thesis that one of his students, Katharina Wirz, 

 submitted in 1950, which exploded Dubois's theory of the seven stages of 

 cephalization. According to Wirz, mammals must, for the time being, be 

 grouped into three classes of cephalic development, the middle class having 

 two sub-divisions. Insectivores, bats and rodents make up the lowest class, 

 terrestrial carnivores make up the lower sub-division of the intermediate 

 class. Pinniped carnivores (e.g. sea-lions), ungulates, all apes and monkeys 

 and Mysticetes make up the upper sub-division, while Odontocetes, 

 elephants and man constitute the highest class (see Fig. 127). Mile Wirz 

 thought that of all Odontocetes the porpoise has the most highly developed 

 brain, followed by the Beluga, the Nai^whal and finally the dolphin. 



Despite the many unresolved problems - e.g. the strange position of 

 elephants on this scale - as far, at least, as Cetaceans are concerned, Mile 

 Wirz's classification agrees by and large with that of Dubois, and with the 

 results of other biologists, such as Quiring (1943). Even though Cetaceans, 

 because of their streamlined contours, have a relatively small body 

 surface, their brains are more highly developed than those of most 

 mammals, Odontocete brains being superior to those of Mysticetes 

 and almost equalling those of man. 



This fact was actually noted by the very first natural scientists to study 

 the brains of porpoises. In 1671 Ray concluded from his studies that these 

 animals must have 'wit and capacity' enough to make Herodotus's story 

 of Arion's miraculous rescue by dolphins (see p. 12) seem credible. The 

 older scholars were reminded of human brains not so much by the size 

 of the porpoise's cerebrum, but rather by the convolutions of its cerebral 

 cortex. (Figs. 126 and 128). These convolutions are not only very striking 

 in appearance, but are an essential criterion for judging the stage of 

 development a given brain has reached. From a number of investigations 

 on mammals it appears that the number of individual convolutions and 

 fissures increases with the size of the brain. This is due to the fact that the 

 grey matter in the brain, i.e. the matter containing the bodies of the nerve 



