640 THE SPOUTING AND MOVEMENTS OF WHALES, 



approaching a circle. The porpoises jump out of the water and 

 describe an elongated curve in the air, descending head foremost, with 

 the body extended. 



The whale dives at once obliquely and disappears for a time longer 

 or shorter, according to the species, but rarely for less than a quarter 

 of an hour. It reappears and spouts very powerfully and long. 



The sounding is characterized, then, among all cetaceans by the fol- 

 lowing peculiarities (1) It commences with an inspiration deeper than 

 any other, and ends with an expiration which is also very strong; (2) 

 the posterior part of the body executes special movements; (3) the 

 whale dives to a great depth; (4) it remains there very long before it 

 appears again. 



E. — THE TRACK. 



Every time a large whale disappears below the surface, it leaves 

 behind it a slick (grasseur), which is especially plain when the water 

 is but little agitated. This ""slick" is unquestionably an extremely 

 thin layer of oil, which spreads on the surface of the water and gives 

 it the well-known mirror-like appearance. This fact has been observed 

 and recorded many times already, and there can be no doubt as to its 

 interpretation. 



It is difficult, however, to understand the origin of this oily sub- 

 stance which the whale leaves behind, for anatomists who have studied 

 the skin of the cetaceans (Delage, 1885; Kiikenthal, 1889; Rawitz, 

 1899, among others) have proved the complete absence of sweat 

 glands or sebaceous glands. The oil can not, then, be derived from 

 secretions of the skin. Inthe common dolphin, a species which I have 

 examined in this particular, the skin is entirely without a trace of oil; 

 it is perfectly dry and does not leave any mark on a well-cleaned glass. 

 It follows, therefore, that this oil must have some other origin. The 

 following observations may, perhaps, put us on the track of the truth. 

 Thiercelin (1866, vol. l)says regarding the southern right whale: "Some 

 little drops of oily matter drop from the spout." If this observation is 

 verified — for it can not be admitted without hesitation — it gives us 

 the source of the "slick" mentioned; but another observation which 

 I made in Gerlache Strait appears to me to supply a more plausible 

 explanation. I noticed at the surface of the water, among the fin- 

 backs and humpbacks of the strait, some irregular masses of a red 

 color surrounded by "slicks." They were without doubt the excre- 

 ments of these animals. The seals and penguins had similar excre- 

 ments, the color of which is explained by the fact that tlie food of 

 these animals consists of JEuphausia (a small thysanopod crustacean), 

 which is abundantly provided with red pigment. The Eu/phausia, like 

 all planctonic animals, possesses lumierous small globules of oil in its 

 tissues, which must serve as floats in animals which pass their lives in 



