98 



The Canadian Field-Naturalist 

 NOTES AND OBSERVATIONS. 



[Vol. XXXIII 



Remarks on the metamorphosis of the 

 Scallop (Pecten ienuicosiatus). — After hatching, 

 the young scallops attach themselves to rocks, scallop 

 shells, or other objects to which they remain as fix- 

 tures for a year or two. I can tell this from num- 

 erous young specimens obtained which possess an 

 aperture through which a portion of the creature 

 protrudes for attachment, and from a few speci- 

 mens I came across which possess an elastic byssus 

 for attachment, which protrudes from the so-called 

 foot, and also from the margins of growth, the 

 striations, and other points of structure which under- 

 go a modification. 



In the earlier stages the byssal attachment appears 

 to agree with that of Anomia throughout the life- 

 history of that genus ; that is, there is an aperture 

 near the apex of the under valve through which a 

 portion of the mollusk itself protrudes, so that it is 

 directly attached to the object. But its agreement 

 with Anomia in this respect is only temporary, for 

 in time the scallop develops a byssus which is of 

 elastic constituency, such as the mussel (Mytilus) 

 possesses throughout its life-history. In the instance 

 of the scallop again this provision is only temporary, 

 for in time as it continues to grow the byssus dis- 

 appears, and the scallop is free and can then move 

 about by the flapping of its valves. 



Sometimes I was able to determine a stage of 

 development from a single example. For instance, 

 the fact that at one time in its life-history the scallop 

 develops an elastic byssus secreted from the foot for 

 attachment to an external object. This I know 

 from only one specimen which had such a byssus. 

 Two other specimens of the same character were 

 obtained, but the byssus of one of them had been 

 broken off in the raking, and it was found lying 

 loose, and the other, a much smaller one, was also 

 detached from the object. 



Considering that the byssus always occurs on 

 the same side of the scallop, and that the aperture 

 of the more immature form extends to the margin of 

 the valve, it is evident that the elastic elongation 

 simply evolves from the original attachment, and 

 that the aperture of the under valve as it becomes 

 obliterated, leaves the scallop, except that it is now 

 moored to an external object, otherwise free. 



Judging from an illustration from Parker and 

 Haswell, these zoologists seem to regard the pectens 

 as hermaphrodite, as they show one part of the gonad 

 in the same individual as male and the other as 

 female. But this is not so, at least in the case of 

 the scallop. The sexes are distinct, and out of 209 

 scallops specially examined by me in my observa- 

 tional work, 100 were males, 108 females, and in 



one the sex was indeterminable. The gonad of this 

 last mentioned was completely empty, not that I 

 consider the scallop hed spawned, for it was im- 

 poverished generally, and apparently in a sickly 

 condition. I might have been able, had I known 

 it at the time, to determine the sex by the digestive 

 organs, but this was a later discovery. This fact, 

 however, helps to emphasize what I say as to the 

 sexes being distinct. The gonad of the male is 

 cream-colored and the stomach and its appendages 

 gray, whereas the gonad of the femcJe is a sort 

 of brick-red color and the stomach and its append- 

 ages brown. 



Andrew Halkett. 



A Robin's Mistake. — A pair of robins have 

 for some years been in the habit of building their 

 nest among the creepers which grow on the side of 

 my house, having for neighbors a pair of crow 

 blackbirds. This year the two nests were placed 

 on either side of a bay window, only a couple of 

 yards apart. Both young families left the nest at 

 about the same time, and this circumstance evidently 

 led to complications. The parent crow blackbirds 

 showed no lack of interest in their young family. 

 On the contrary, for the first day or two after the 

 latter left the nest the old birds resented the appear- 

 ance of anyone on the lawn where the young were, 

 complaining loudly and making savage darts at the 

 intruder, as though intending to do him grevious 

 bcdilj' harm. Nevertheless, in spite of all this 

 parental solicitude, one of the young crow black- 

 birds was adopted by one of the parent robins. 

 How it originally came about I do not know; but a 

 few days later, when all of the other members of 

 both familes had disappeared, I was attracted by 

 the novel sight of the robin working industriously 

 early and late to satisfy the voracious appetite of 

 his adopted progeny, who followed him about con- 

 tinually demanding more. This proceeding con- 

 tinued for about three weeks and as the pair re- 

 mained all that time in my garden, I was able to 

 keep close watch on them and to note the gradual 

 growth of the young blackbird, until when I last 

 saw them he was fully plumed and almost indis- 

 tinguishable from an adult. There was, therefore, 

 no doubt whatever as to the correctness of the 

 identification. It was not, as some might be in- 

 clined to suggest, a cow bird, but unquestionably 

 a crow blackbird. Once, on the second or third 

 day of my observations a pair of adult crow black- 

 birds — ^possibly the real parents — arrived on the 

 scene and for a time evinced considerable excite- 

 ment over their "lost heir," but as the latter took 



