136 - MICHIGAN ACADEMY OF SCIENCE. 



5. Wfmt is tJw length of time occupied in spawning f 



Dean, on what evidence is not clear\, believes that the "spa^vTiing- oc- 

 cupies considerable time" and conjectures that in some cases as many as 

 twelve hours are thus consumed. ''In this" remark Whitman and 

 Eyclesh^'uier "he is probably much mistaken." Again they say: "That 

 the average period of deposition is brief, can hardly be doubted, since 

 in most cases the eggs of a nest are found in the same, or nearly the 

 same, stage of development." 



In several nests I have found eggs in cleavage stages varying from 

 two to sixteen cells. According to the table given by Whitman and 

 Eycleshymer, to show the time occupied in development, there is an 

 interval of about three hours between the two cell and the sixteen cell 

 stage. In these cases then the deposition of eggs must have occupied 

 this yjeriod at least. Additional evidence is given under the sixth head 

 below. 



As development proceeds diiferences of a few hours in the age of the 

 eggs in a nest are not at all noticeable — so that all the eggs from a nest 

 appear to be in the same stage. In the cleavage stage, on the other 

 hand, differences in age may be measured with great accuracy. 



I have twice found nests which contained two sets of eggs of widely 

 different stages. In one of the cases my record showed that the nest 

 had been spawned in and then abandoned, to be subsequently spawned 

 in by a second fish. 



6. TJie method of spiiicniiKj. 



Having built his nest the male guards it and I have several times 

 seen males leave their nests in order to drive other males from the 

 neighborhood. On such occasions the males frequently fight fiercely,^ 

 so that one often finds them at the spawning season with portions 

 of the fins bitten away or strips of the skin torn from the sides. The 

 male thus holds the nest until a female arrives, when the spawning 

 begins. This may occur at any time of day or night. The females 

 lies in the nest and the male circles about her head, frequently stopping 

 to bite her gently on the snout or sides. These maneuvers continue 

 for ten to fifteen minutes. The male then places himself b}' the side 

 of the female and there is a violent agitation of the fins of both, dur- 

 ing which the eggs and milt are emitted. This continues for the frac- 

 tion of a minute. The circling movements are then again resumed to 

 be followed by a brief interval of spawning. In one case the spawn- 

 ing was observed for an hour and forty minutes, and during this time 

 four or five batches of eggs were laid. At the end of this time the nest 

 contained but few eggs. Upon returning to it next morning many more 

 eggs were found in it, so that the whole time of spawning was u^doubt- 

 edl.y several hours. 



I may add here a single unrelated observation. The eggs in this local- 

 ity are much lighter in color than those figured by Whitman and 

 Eycleshymer — so that the nests maij he very conspicuous when first built 

 — easily seen at a distance of twenty or thirty feet. Later the eggs 

 grow darker and the nest itself less conspicuous. Often, however, even 

 when first built the nests are concealed by logs, stumps, bushes, or the 

 floating stems and leaves of cat-tails, and are then very difiicult to find. 



