EVOLUTION AND EXTERNAL APPEARANCE 85 



Whale, an animal some 1 7-26 feet long, found in all warm and temperate 

 seas. Though some individuals are, in fact, countershaded, the front of 

 the body at least of the majority of these dolphins is white on top and dark 

 at the bottom. The Pilot Whale, which is entirely black, may well owe 

 this peculiarity to its being a nocturnal animal (cf. Chapter 6). Albinos, 

 i.e. completely white or creamy-white specimens, are also found in 

 Cetaceans, just as they are in other inammals. I myself came across an 

 albino Bottlenose Dolphin near Harlingen, and on 19th April, 1957, a 

 white Sperm Whale was killed off Japan - a reincarnation of the famous 

 Moby Dick. 



While the two sexes in Cetaceans do not differ in colour, they often 

 differ in length. It seems that in Mysticetes, the average female is 3-6 feet 

 longer than the male, while the female Odontocete is shorter than her 

 mate. As a rule, however, the difference is smaller than in Mysticetes, and 

 in porpoises, for instance, there seems to be no difference at all. In young 

 porpoises, the male is probably longer, but in mature animals the reverse 

 is the case. In other species, e.g. in Sperm Whales, Bottlenose W^hales, 

 Killer Whales and False Killer Whales the difference between males and 

 females is about 19, 13, 8, and 3 feet respectively. Ziphiids of the genera 

 Berardius and Ziphius form the exception, for the males are shorter. In 

 some species, there is moreover a clear difference in shape between the 

 sexes. Thus male Bottlenose Whales have a more protruding forehead 

 than females, male Killers have a much larger dorsal fin, the two sexes of 

 the Bottlenose Dolphins have differently shaped dorsal fins, and the tooth 

 of the male Narwhal has already been mentioned. 



A careful look at the skin of inany dolphins will reveal the presence of 

 a number of long parallel stripes (Fig. 100). The distance between the 

 stripes agrees exactly with the distance between the animal's teeth, and 

 we may therefore infer that they have resulted from fights with members 

 of the same species. Such stripes are also found on Sperm Whales, where 

 the distance between them is 4-8 inches, i.e. the exact distance between 

 their teeth. But Baleen W'hales, too, have scratches on their skin, which 

 cannot possibly be due to wounds inflicted by members of the same 

 species, which, as we know, have no teeth. In fact, these scratches do not 

 run parallel, but fan out in all directions. They are possibly due to abrasions 

 caused by ice-floes. Impressions inflicted by the suckers of squids are com- 

 monly found on Sperm W^hales and those dolphins which feed on squids, 

 e.g. the Pilot Whale and Risso's Dolphin. 



Our attention is fiequently arrested by peculiar scars, often with a 

 radiating pattern, found particularly on the skin of Blue Whales, Fin 

 Whales and Sei Whales. These round, oval or crescent-shaped skin 



