360 
MESSRS. E. M. BALFOUR AND W. N. PARKER ON TJIE 
Introduction. 
The following paper is the outcome of the very valuable gift of a series of embryos 
and larvae of Lepidosteus by Professor Alex. Agassiz, to whom we take this oppor¬ 
tunity of expressing our most sincere thanks. The skull of these embryos and larvae 
has been studied by Professor Parker, and forms the subject of a memoir already 
presented to the Poyal Society. 
Considering that Lepidosteus is one of the most interesting of existing Ganoids, 
and that it is very closely related to species of Ganoids which flourished during the 
Triassic period, w r e naturally felt keenly anxious to make the most of the opportunity 
of working at its development offered to us by Professor Agassiz’ gift. Professor 
Agassiz, moreover, most kindly furnished us with four examples of the adult Fish, 
which have enabled us to make this paper a study of the adult anatomy as well as of 
the development. 
The first part of our paper is devoted to the segmentation, formation of the 
germinal layers, and general development of the embryo and larva. The next part 
consists of a series of sections on the organs, in which both their structure in the 
adult and their development are dealt with. This part is not, however, in any sense 
a monograph, and where already known, the anatomy is described with the greatest 
possible brevity. In this part of the paper considerable space is devoted to a com¬ 
parison of the organs of Lepidosteus with those of other Fishes, and to a statement 
of the conclusions which follow from such comparison. 
The last part of the paper deals with the systematic position of Lepidosteus and of 
the Ganoids generally. 
General Development. 
The spawning of Lepidosteus takes place in the neighbourhood of New York about 
May 20th. Agassiz (No. 1)* gives an account of the process from Mr. S. W. Garman’s 
notes, which we venture to quote in full. 
“ Black Lake is well stocked with Bill-fish. When they appear, they are said to come 
in countless numbers. This is only for a few days in the spring, in the spawning season, 
between the 15th of May and the 8th of June. During the balance of the season 
they are seldom seen. They remain in the deeper parts of the lake, away from the 
shore, and, probably, are more or less nocturnal in habits. Out of season, an occasional 
one is caught on a hook baited with a Minnow. Commencing with the 20th of April, 
until the 14th of May we were unable to find the Fish, or to find persons who had 
seen them during this time. Then a fisherman reported having seen one rise to the 
surface. Later, others were seen. On the afternoon of the 18th, a few were found 
on the points, depositing the spawn. The temperature at the time was 68° to 69° 
* The numbers refer to the list of memoirs of the anatomy and development given at the end of this 
memoir (p. 433). 
