784 MR. D. O. LILLIE OX THE ANATOMY [jMi^}' '^^, 



size, with those figured and described by Mr. CoUett* as occurrin<T 

 in J), burealis. Tlie spots in Ji. mascalas usii;ill\ did not exceed 

 50 nun. in lenf;th. 



Tliroui-yrooces. — In several indivichinls of ])o\\\ B. mtisculas and 

 ]'). nihhaldii the skin lining the grooves in the throat-region had a 

 ])right red appearance. It unfortunately did not occui' to nie at 

 the time to ascertain the cause of this ; but I am inclineil to 

 think that the red colour of the grooves may be due to their 

 being very highly vascidar, and thus heli)ing to aerate the blood. 

 The throat-grooves of Balcenoptera occupy about half of the 

 ventral surface of the body, extending from the anterior end of 

 the mandible to the navel. In B. musculus there are about 100 

 of these grooves, in the other species about 60. The skin lining 

 the f uiTows is extremely elastic. When unextended t!ie grooves 

 are about an inch in width ; when extended they are often 

 six inches wide. Thus they would give a large aerating surface. 

 Undoubtedly the principal function of these elastic furrows on 

 the throat is to inci-ease the size of the mouth-cavity, so that a 

 large volume of water containing Crustaceans can l)e taken in at 

 each mouthful. The water is strained off through the whalebone 

 plates, and afterwards the food is swallowed. In Balania the 

 mouth itself is very large, owing to the arched form of the skull, 

 so that its capacity is natuially ample. Hence the absence of 

 throat-grooves in the Right Whales. The function of the grooves 

 as an aerating surface or external gill, if it occurs at all, would 

 be a secondary one. This theory, however, would enable us to 

 understand the ext)-aordinary powei's of I'emaining under water 

 attributed to Balcenoptera wliich will be referred to later in this 

 paper. 



Jacobson's organ. — On the under surface of the snout, about half 

 way between its extren)e tip and the small anterior filaments of 

 whalebone, there wei'C two small apertun s leading into luurow 

 tubes which ended blindly about two inches from their mouths 

 (text-fig. 75). These were the ducts of the organ of Jacob.son. 

 In B. sibhcddii they are only represented by two .small depressions. 

 In most Mammals these organs communicate with the no.strils, 

 but in an adult B. inaseulus they ai-e separated fiom the nostrils 

 by a distance of some ten feet, and are interesting examples of the 

 persistence of traces of an organ aftei- it has become obsolete. It 

 is just ])Ossible that the small ducts in B. mascuhiti may have 

 sonic function, but they were not equally well developed in all the 

 individuals examined, and in one specimen they were reduced to 

 mere depre.«.sions very much like those of B. .sibhaldii. 



Testes. — In a member of this species, 51 feet long, the testes 

 were measured and found to be only i) inches in length and 3 inches 

 in diameter. Jn a specimen (50 feet long the testes were 2 feet 

 (i inches in length and nearly a font in diameter. This. shows that 

 m.'ile members of this species reach maturity when between 50 and 

 60 feet long. 



• Troc. Znol. Soi-. IPSR. p. 'JIO. pi. \xm. H-. -.L. 



