MB. T. SOUTHWELL ON THE REPRODUCTION OF THE COMMON EEL. 2G3 
of generation in the Eel takes place in salt water, and in the 
autumn they accordingly proceed to the sea. (2) This development 
takes place in the deep sea, not near the coast, and is probably 
rapidly accomplished. (3) The young fry develop to the mature 
form on the spawning beds, and ascend the rivers as “ elvers ” in 
the spring. (4) lie was also of the opinion that the rapid 
development of the reproductive organs of the old iish exhausts 
them to such an extent that they die soon after having spawned. 
Jacoby’s investigations, although a great advance upon what had 
previously been known with regard to the life-history of this fish, 
still left open to conjecture, the events which took place during the 
period that intervened between its retirement to the salt sea and 
the return of the offspring in the elver form, and nothing was 
known by actual observation of the ova and the early stages of its 
development. That this ignorance with regard to so important 
a period in the life-history of so common a fish was a reproach to 
modern naturalists goes without saying, but the difficulties in the 
way of further investigations seemed insuperable, and have now 
only been overcome through the existence of a physical peculiarity 
in the tidal currents in a portion of the Mediterranean Sea, the 
nature of which will be explained further on. This circumstance 
was fully utilised by Professor Grassi and l)r. Calandruccio of 
Home, who by means of material received from the Strait of 
Messina, have been enabled to trace the development of the ova of 
the Eel through all its stages, and although the entire series of 
changes have not been witnessed in the same individual, the 
material at their disposal has been so abundant as to leave no 
doubt whatever as to the correctness of their conclusions. 
The confusion which has arisen with regard to the Common 
Eel is a most instructive example of the dangers attending what 
may be styled the purely empirical method, i.e., descriptions of 
specimens “simply as they appear,” by which imperfect means 
“ different forms are called different species without any 
consideration of the relations they bear to each other, and 
without regard to such questions as : are the specimens adult or 
larval? or, may not many of the different forms be the same 
animal at different ages or in different sexes?”* 
# Cunningham, "Larva of the Eel,” Jour. Marine Bio. Ass., new series, 
vol. iii. p. 279. 
VOL. VI, T 
