Book Description

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1913 edition. Excerpt: ... p. 583), but Mayer (1910) has already pointed out that the number of tentacles to the octant in the type species lactea L. Agassiz may be more than five, and in a considerable number of lactea, and as the following table shows, it is the rule, not the exception, to find more than five tentacles to the octant. On examining the individual octants it was at once evident that when there were only five tentacles, the ones nearest the ocular lobes were usually the youngest; but when there were more, the others were irregularly interpolated. This, of course, shows that it is impossible to distinguish Kuragea with seven, from Dactylometra with five tentacles to the octant; and as we do not yet know what the limit to tentacle formation is in D. lactea, we may define Dactylometra as Pelagidae with five or more tentacles to the octant. The various species of Dactylometra are distinguished from one another only by such minor characters as color, number of tentacles, and form of the marginal lappets, features all more or less variable. The Pacific forms, ferruginaster Kishinouye and pacifica Gotte, are undoubtedly merely successive stages in the development of one species (Maas, 1909), in which, as the present collection shows, five tentacles per octant are attained in specimens of about 40 mm. in diameter. In large specimens of this species accessory tentacles appear (D. longicirrha Kishinouye), and in its final condition there are seven tentacles per octant Kuragea depressa Kishinouye). According to Kishinouye, the tentacles are short in ferruginaster, long in pacifica ( = longicirrha Kishinouye), but my series of lactea and the Japanese Dactylometras in the present collection show that there is too much variability in this respect and that it is...