M. A. Miiller on the Development of the Lampreys. 301 



and otolithcs, although these only persist in the small Lamprey. 

 With regard to the Sea Lamprey he could ascertain nothing. 



It appears from his observations that the duration of the 

 larval existence must be three years. The spawning takes place 

 in the spring, and only once in the year. In May he took six 

 Ammocoetes ; three small ones, measuring on an average about 

 2'f inches, and weighing on an average Qy grains, and the other 

 three measuring about 6 inches, and weighing on an average 87 

 grains. The three first must have been those of the preceding 

 year, the larger ones must have been two years old ; and as they 

 showed no trace of metamorphosis, they could not have pro- 

 duced perfect Lampreys until the third year. Large individuals 

 of Ammocoetes also occur after the time of the metamorphosis, 

 and these probably do not undergo their change until the fourth 

 year. In the perfect state, the Lampreys live a very short time. 

 Immediately after the spawning season they disappear entirely, • 

 and their dead bodies may be seen floating in the water, the 

 ovaries of the females being quite empty. This long duration 

 of the larval state is remarkable, as in the only other Vertebrata 

 which undergo a metamorphosis (the Batrachia) this usually 

 takes place at an early period, and the animal continues to grow 

 long after it has acquired its mature form. The metamorphosis 

 of the Lampreys, therefore, resembles that of the Insects, in 

 which the larval period is the most important portion of the 

 animal's existence, — its principal business in the perfect state 

 consisting in providing for the continuance of the species. 



In conclusion, the author refers to the doubts which these 

 observations may induce as to the systematic position of the 

 Lampreys. In the occurrence of the metamorphosis, and the 

 complete segmentation of the yelk, they resemble the Batrachia ; 

 and they also differ from the Fishes in the occuiTence of a pair 

 of elastic swellings in the hulbus arteriosus, one above each semi- 

 lunar valve, whilst the inner wall of the bulb is destitute of the 

 trabecular system which is generally present in Fishes. The 

 structure of the brain also is different from that prevailing 

 amongst the Fishes ; but, according to the author's views, the 

 nature of the dorsal chord and its appendages is decidedly piscine. 

 The result of his examination of comparative characters is, in 

 fact, to leave the Lampreys exactly in their former position. 

 He promises a longer memoir on this subject, illustrated with 

 figures. 



