200 BOTTLENOSE PORPOISE TRUE. 



foetuses found at any specific date, as well as the young, vary consid- 

 erably in size. Several of the females captured during my stay at 

 Hatteras contained large foetuses, but they were not all of the same size. 

 Two foetal skulls which I obtained on the same day measure 240 and 163 

 millimeters in length respectively. We have also noted above that the 

 young individuals in the schools examined varied greatly in size. 

 From these facts it would appear that although the birth of the young 

 may be said in general terms to take place in spring, the breeding 

 season extends over a considerable period. It is a well-known fact 

 that among the terrestrial mammalia the southern representatives of 

 those species which have an extensive range north and south breed 

 earlier in the year than the northern representatives. Analogically it 

 seems probable that the porpoises which habitually resort to the most 

 southerly localities in autumn breed earliest in spring, while those that 

 remain in more northerly parts during the winter breed later. 



If this supposition is correct, it accounts perhaps for the disparity 

 in age of the individuals in the different schools. One can readily 

 imagine that during a migration individuals from diflferent localities 

 would meet and journey together, and that the young in quite different 

 stages of development might be found in the same school. 



The nursing females, as well as the gravid ones, are recognizable by 

 the increased size of the abdominal region, due to the enlargement of 

 the great milk glands. 



The largest porpoise taken at the Hatteras fishery was 12 feet in 

 length and yielded 24 gallons of oil. The average yield in winter is 

 about 8 gallons, but the amount falls to 3 or 4 gallons later in the 

 season. 



My attention having been drawn to the question of the correlation 

 between the condition of the teeth, the navel, and the hairs on the lip 

 in young individuals, I made some special observations in the case of 

 the five youngest porpoises captured May 19. The results obtained 

 were as follows: 



(1) Female.— Length, 3 feet 7* inches. Color dark ; lips dark. The 

 lower portion of the shafts of the hairs were present, and projected 

 slightly above the skin. No teeth had pierced the gums. The navel 

 was indicated by a simple, distinct fissure about 1 inch long; its lateral 

 margins were not raised above the surrounding integument. 



(2) Male.— Length, 4 feet 5i inches. Color light. The hairs had 

 dropped out, leaving conspicuous depressions in the skin. No teeth 

 visible. Umbilical fissure open, but only about one-fourth of an inch 

 in length. 



(3) Female.— Length, 5 feet 8 inches. Color light. Depressions 

 marking the position of the hairs less conspicuous than in the last in- 

 dividual. Umbilical fissure obliterated. The teeth had pierced the 

 gums, and protruded about a quarter of an inch ; their crowns were 

 sharp pointed. 



