. â 100 SC^ 32 34 36 384042 44 46 48 SO 52 54 5658 60 62 64 66 LENGTH RANGE I 2 3 4 5 6 7 STAGE d* I 2 3 4 5 6 7 STAGE $ Fig. 53. Sexual dimorphism and developmental condition of the sexes in a fully adult swarm of E. superba, showing dominance of the female in a sample from St. WS 915. Developmental condition of the sexes In Table 19 of Bargmann's appendix it is repeatedly shown that, except in the very young mixed larval and adolescent swarms encountered from August to November, the dominant state of sexual development in the male is normally one or two stages, sometimes more, ahead of the c
. â 100 SC^ 32 34 36 384042 44 46 48 SO 52 54 5658 60 62 64 66 LENGTH RANGE I 2 3 4 5 6 7 STAGE d* I 2 3 4 5 6 7 STAGE $ Fig. 53. Sexual dimorphism and developmental condition of the sexes in a fully adult swarm of E. superba, showing dominance of the female in a sample from St. WS 915. Developmental condition of the sexes In Table 19 of Bargmann's appendix it is repeatedly shown that, except in the very young mixed larval and adolescent swarms encountered from August to November, the dominant state of sexual development in the male is normally one or two stages, sometimes more, ahead of the corresponding state in the female. The advanced state of the male, as Figs. 50-2 show, persists throughout the greater part of the life of the swarm up to the point of pairing, when as might be expected swarms in which both males and females are dominantly at stage 7 are not uncommonly encountered. An ingenious device has recently been constructed by Vittorio and Livia TonoUi (1958) and used to study the form and internal structure of plankton patches in the Italian lakes. It could well, it seems, be employed with advantage in future studies of the biometrics of krill swarms, with especial reference perhaps to the larval swarms. A rather long plankton net ends in a polysthyrol tube that reaches the boat. The tube is here connected to a turbidi- meter, from which another tube runs into a metallic box, where a controlled aspiration can be exerted. The water, containing plankton filtered by the net, ascends through the polysthyrol tube, and, flowing through the turbidimeter, enters the vacuum box. In this way, by regulating both the speed of the boat and the aspiration to a constant value, we can obtain, through the variation of the turbidity values, an indication of the density of the particles suspended in the layer where the net is fishing. In the vacuum box we have twenty vials, each provided with a filtering window. When we are warned that the net has reached a patch of plank
Size: 1784px × 2801px
Photo credit: © The Bookworm Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, booksubjectocean, booksubjectscientificexpediti
