ABSTRACT
In the last volume of the ‘Zeitschr. f. wiss. Zool.’ (vol. liv, 1892, p. 569) a paper appeared entitled “Ueber Anomalien der Segmentierung bei Anneliden und deren Bedeutung für die Theorie der Metamerie,” by C. J. Cori, dealing chiefly with the intercalation of half-segments, and with cases in which the furrows dividing successive segments externally have become continuous, thus forming a spiral going once, or more than once, round the body of the animal. Cori found seventeen out of about two hundred common earthworms (Lumbricus terrestris) abnormal in one of these two ways. He also found one specimen of a Lumbriconereis, one of Halla parthenopeia, one of Diopatra neapolitana, and one of Hermodice carunculata with intercalated parts of segments. He does not mention, however, how many specimens of each of these species he examined, and from his account one is naturally inclined to look Upon such occurrences as rare, and to call them, with him, abnormalities. It may, therefore, be worth while to point out that there is at least one family of Polychætes, judging from over eighty specimens coming from different parts of the world, in which cases of intercalation and of spiral segmentation are so common as to be regarded rather as normal individual variations than as abnormalities. This family, from which Cori gives but one example, is the Amphinomidæ, and the genus in which such variations particularly occur is the genus Amphinome (Blv.), Briig, in its widest sense,—including, therefore, the genera Eurythoe and Hermodice of Kinberg and the genus Lino-pherus of Quatrefages, as well as Amphinome s. str. Knb.
The description of the spiral given in this column applies when the animal is viewed from the dorsal surface with its anterior end in front.
Pl. XLII, fig. 1.
Pl. XLII, fig. 2.
Segments 38—41 are also irregular on the dorsal surface in this specimen.
When the same specimen has more than one kind of irregularity it occurs more than once in the list, but is referred to by the same number.
Tbe spiral in this specimen is interrupted in the middle by the irregularity in Segments 35—41.
I should mention that the specimens were not intended for histological work, but only for museum specimens, and as such all the Amphinomes in the Madras collection are very well preserved considering how difficult Polycheetes are to preserve well.
This is a true spiral, though a short one, and not an intercalated halfsegment, for the furrow has a spiral course (see fig. 7). The same holds for the three quarters of a round in spec. 4.
See foot-note, p. 537.
The parapodia on the right side of Segments 115—118 had been previously removed in this specimen, evidently by some one who had noticed the peculiarity. I cannot, therefore, be certain where the spiral ends.
An interesting paper by T. H. Morgan on the same subject as the above, but dealing chiefly with Oligochaetes, has recently appeared in the ‘Journal of Morphology,’ vol. vii, Nov., 1892, pp. 245—251. As that number of the journal had not arrived here when my paper was sent to press, I have been unable to introduce the results contained in it; but the editor of this journal kindly called my attention to it on receiving my manuscript, and I give the reference for the convenience of those interested in the subject.
