I082 BUIvLETIN OF THE BUREAU OF FISHERIES. 



with black eyes and free tails. Instances of two or three stages in the eggs of a 

 nest might be multiplied, but the general statement may be made that when 

 such large numbers of eggs are found in a nest they are in more than one stage 

 of development and have been laid by more than one female. 

 Orientation of the embryos. — Ryder stated (1887) that — 



The young adherent embrj'os are found tohave their heads directed toward the 

 opening of their retreat and their tails toward its blind and dark extremity. This 

 appears to be invariably the case, and it would seem that the direction from which the 

 light comes, in this instance, at least, has a great deal to do in determining the direction 

 of the axis of the body of the future embryo. This position of the young iishes is main- 

 tained as long as they are attached. 



The last of these statements is correct, but the others are erroneous. In 

 scores of nests which the writer has examined the embryos are found pointing 

 in all directions. This is especially so in nests which are equally lighted from 

 all sides, i. e., the board nest mentioned above. In a nest on the under side of 

 a log projecting from a bank, eggs were found with the embryos pointing in all 

 directions, but the majority had their heads turned more or less toward the 

 point of greatest illumination. In Pinna shells, as shown in figure 7, plate ex, 

 the embryos are almost always turned away from the opening of the shell toward 

 the hinge. The writer is in position to state that only in a very general sense 

 is it true that the embryos have any definite direction of axis, and not "invari- 

 ably, " as stated by Ryder. Figures 9 and 10, plate cxi, photographs of different 

 nests, show this. Pieces of wood, i by 2 inches, from the log above mentioned 

 have embryos pointing in as many as nine different directions. In her earliest 

 paper (1891), Miss Clapp quotes Ryder, and adds: ^ 



It was observed during the past summer that the embryos within the egg membrane 

 do not have their heads all turned the same way, but in every possible direction, and it 

 is only after the young toadiish are hatched that the heads of the whole brood are turned 

 in the same direction. 



That this latter statement is incorrect a glance at figures 7, 8, 9, 10, and 11, 



plates ex, CXI, and cxii, will show. Smith (1885), in the paper previously 



referred to, says on this subject: 



In the species of Lcpadogaster the embryos show a marked irregularity of position; 

 that is, the eggs are affixed to their station regardless of the future growth, which may 

 develop with its head or tail in any direction with reference to the place of attachment. 



In a paper published in 1890, Ryder, basing his argument on his (incoinplete 



and erroneous) observations that all the embryos of a brood conform in direction 



to one axial plane, the heads pointing toward the light, declares that the polarity 



of the young is determined while the eggs are still in the ovisac of the mother. 



That this is not true the experimental work of Miss Clapp, as set forth in her 



papers of 1891 and 1899a, proves absolutely. If further evidence is needed, 



the reader is referred to the various photographs in this paper in which embryos 



early and late are shown. 



