Discovery reports (1959) Discovery reports discoveryreports29inst Year: 1959 332 DISCOVERY REPORTS the loss of four and two spines, respectively. Of these ninety-one fifth furcilias ten moult to sixth furcilias, whereas eighty-one miss out this three-spined stage and moult directly to the one-spined seventh furcilia. The nineteen sixth furcilias that have moulted from both fourth and fifth furcilias also moult to seventh furcilias. There are, then, three alternative routes from fourth to seventh furcilias, 4-5-6-7; 4-6-7; 4-5-7, and it is the last of these that the majority of larvae follow.
Discovery reports (1959) Discovery reports discoveryreports29inst Year: 1959 332 DISCOVERY REPORTS the loss of four and two spines, respectively. Of these ninety-one fifth furcilias ten moult to sixth furcilias, whereas eighty-one miss out this three-spined stage and moult directly to the one-spined seventh furcilia. The nineteen sixth furcilias that have moulted from both fourth and fifth furcilias also moult to seventh furcilias. There are, then, three alternative routes from fourth to seventh furcilias, 4-5-6-7; 4-6-7; 4-5-7, and it is the last of these that the majority of larvae follow. Table 8. Variation in the number of terminal spines on the telson lost during ecdysis of the fourth and fifth furcilias No. of No. of terminal \rcilia stage terminal spines spines in next stage No. specimens examined 4 4 7 7 5 3 129 12 91-4 8-6 Total 141 lOO-O 5 5 5 5 3 I Total II 88 99 III 88-9 loo-o F7 100 Fig. 14. The paths of development of one hundred fourth furcilias calculated from the percentages of fourth furcilias moulting to fifth or sixth furciUas and the percentages of fifth furcilias moulting to sixth or seventh furcilias (see Table 8). The figures show the arrangements of the spines on the telson in each stage and it can be seen how the number of terminal spines in the succeeding stage is determined. Although it is now accepted that, within one species, larvae with certain combinations of setose and non-setose pleopods tend to be dominant and that the few other combinations that occur can be considered as variants, it is unusual for any of the furcilias which are recognized by the number of terminal spines on the telson, to be omitted. This point is emphasized by Boden (1955, p. 375) who,
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