A very characteristic feature of certain Whales are the furrows {345} to be seen on the throat. This is especially the case with the Rorquals, in which group the Humpback Whale, _Megaptera_, is to be included. The whales of these two genera (_Balaenoptera_ and _Megaptera_) have a large number of the throat furrows--as many as sixty have been counted. Some other Whales have a smaller number; thus _Rhachianectes_ has but two on each side, and the Physeteridae have not many more. These furrows are absent in very young embryos. It is thought by Professor Kuekenthal that they allow of a wide opening of the mouth. [Illustration] FIG. 181.--Dorsal surface of bones of right anterior limb of Round-headed Dolphin (_Globicephalus melas_). x 1/10. The shaded portions of the digits are cartilaginous. _c_, Cuneiform; _H_, humerus; _l_, lunar; _R_, radius; _s_, scaphoid; _td_, trapezoid or magnum; _U_, ulna; _u_, unciform; _II-V_, digits. (From Flower's _Osteology_.) The blow-hole of Whales is, of course, the aperture of the nostrils, which are not so far back in the foetus as in the adult. By the characters of the nostrils the Toothed Whales can be distinguished from the Baleen Whales; in the latter the orifice is double, in the former single. In embryos of Dolphins, however, the two apertures are quite independent. The phenomena of spouting have often been misinterpreted.[231] When the Whale breathes, the expired air rushes out through the nostrils. The water vapour in the breath condenses into drops of water in the cold Arctic regions where the phenomenon has been mainly observed. Hence the idea that water taken in at the mouth is expelled through the blow-hole. As the Whale approaches the surface to breathe, it may be that some of the water of the sea is {346} driven upwards by the forcible expulsion of air from the lungs. But for the most part the water which is spouted is simply condensed breath. Like some, but not all, other aquatic Mammalia the Whales have apparently no external ear. Indeed the opening of the ear is excessively small. In a huge Rorqual it will "admit a quill"; and although "a quill" is rather vague, we may fairly allow any sized quill without proving that the orifice of the auditory passage is anything but exceedingly minute. As a proof, added to so many, that the Whales are the progeny of terrestrial creatures, we have the occasional traces of external ears.[232] [Illustration] FIG. 182.--Left lower jaw of foetus of _Balaenoptera rostrata_. Inner aspect, natural size, showing teeth. (After Julin.)