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Show 1890.] REPETITION OF PARTS IN ANIMALS. 587 of a Herring. From these points of structure Mr. Day concluded that the specimen was a hybrid between the Herring and the Pilchard. Before discussing the propriety of this view, I will describe two specimens showing somewhat similar characters, which were given to me by Mr. Dunn during the summer of 1889. Mr. Dunn told me that among the large number of Pilchards which come under his notice as director of the pilchard-curing factories at Mevagissey, specimens showing this singular reduplication of the scales on one side are not uncommon. Owing, however, to the fact that the fresh Pilchards are shovelled wholesale into the brine-vats, it is generally not until the fish are picked over for packing after the salting process that any individual peculiarities are noticed. This was the case with the present specimens, which were given to me as they came salted from the presses. Nevertheless, when received, they were in good condition. The first specimen measures 8 inches to the base of the caudal fin. The head and opercula of both sides are normal. The number of scales along the lateral line on the left side is 32, and the number on the right side is 56 or 57. Examined closely, it can be seen that for the distance of about an inch behind the operculum the scales are not much smaller than those of the normal Pilchard, but that behind this point each scale is of about half the normal size. The second specimen differs from the first in that the reduplication occurs on the left side instead of on the right. Furthermore, the scales are normal in size as far as the anterior end of the dorsal fin, behind which place they are of about half the normal size. The transition is much more abrupt in this specimen than in the other. The scales of this fish had been somewhat rubbed, and I was not able to satisfy myself of the accuracy of the counting, but the total number along the lateral line was approximately 48. In the figure of Mr. Day's specimen, given in P. Z. S. 1887, pi. xv., no transition is indicated between normal and abnormal scales, but there is a general appearance of uniformity. These three specimens all agree in showing repetition of the scales on one side. The distance to which this repetition extends differs in each case, but in all the condition of the scales is uniform and regular so far as it extends. In m y judgment these specimens should be considered as examples of variation in number of parts. Since, however, it has been suggested that they are of hybrid origin, a few words may be permitted in criticism of this view. No direct evidence is adduced which points to hybrid parentage. The suggestion is derived from (1) the condition of the scales, (2) the number of the gill-rakers, (3) the alleged difference in the opercula of the two sides. In view of the first point, viz. that the number of the scales on one side is intermediate between that of the Pilchard and that of the Herring, it seemed desirable to know whether the resemblance extended to the minute structure of the scales or was restricted to their number only. On comparing microscopically the scales of the Pilchard and the Herring, I find |
