B. Yl.] THE HISTORY OF ANIMA.1,8. 151 



their mutual differences, and the manner of the develop 

 ment of their ova. 



8. At the season of sexual intercourse, th3 seminal ducts 

 of the male are full of fluid, so that a white matter escapes 

 when they are pressed. These passages are divided, and 

 originate in the diaphragm and the large vein : at the same 

 season the passages of the male are conspicuous, and may be 

 compared with the uterus of the female. When it is not 

 the season of sexual intercourse, they are less conspicuous, 

 from not heing in use. In some fish, and sometimes, they 

 are not visible at all, as it was remarked of the testicles of 

 birds. The seminal and uterine passages are different in 

 other respects also, and because those of the male are at 

 tached to the loins, those of the female are easilv moved, 

 and enclosed in a thin membrane. The nature of the pas 

 sages of the male may be seen in works on anatomy. 



9. The selachea become pregnant again while with young, 

 and the period of gestation is six months. Among the galei, 

 the asterias produces young the of tenest ; for it produces 

 twice in a month : it begins to copulate in the month of Sep 

 tember. All the other galei except the scylia produce twice 

 in the year ; the scylia but once. Some of them have their 

 young iu the spring. The rhine produces its first brood in 

 the spring, and its last in the autumn, near the winter season, 

 and the setting of the Pleiades. The second fry are the most 

 numerous. The narca produces its young in the autumn, 

 The selache descend from the ocean and deep water to the 

 shore, to produce their young, both for the sake of the 

 warmth, and care of their offspring. 



10. No other fish but the rhine and the batos have ever 

 been observed to unite with others not of their own kind, 

 but there is a fish called the rhinobatus, which has the head 

 and upper part of the rhine, and the lower part like the 

 batus, as it were made up of both. The galei and the 

 galeoeides, as the alopex, dog-fish, and the flat fish, as the 

 narce batos, leiobatos and trygon, are :n this manner ovovi- 

 parous. 



CHAPTER XI. 



1. TIIK dolphin, whale, and other cetacea which have a 

 biow-hole but no gills, are viviparous, and so are the 



