The life of crustacea / by W.T. Calman.

  • William Thomas Calman
Date:
1911
Catalogue details

Licence: In copyright

Credit: The life of crustacea / by W.T. Calman. Source: Wellcome Collection.

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    to the Lobsters, yet the difference in their mode of development is even more pronounced. Instead of beginning life as minute pelagic zoeae, they leave the shelter of the mother’s abdomen as perfectly-formed little Crabs (Fig. 31). Amongst the Decapoda, instances of direct develop- ment like those just described are exceptional, but in some of the other orders of the Malacostraca direct development is the rule. In the great division Peracarida, as we have already seen, the females are Fig. 31 —Young Specimen of an African River Crab {Potamon johnstoni), taken from the Abdomen of the Mother. Much enlarged The adult of an allied species is figured on Plate XXV provided with a pouch, or marsupium (from which the name of the division is derived), in which the eggs are carried. Within this pouch the young undergo the whole of their development, and they only leave it, as a rule, when they have attained the structure of the adults. Among the more familiar representatives of this division, the Sand-hoppers (Amphipoda), the Woodlice (Isopoda), and the Opossum Shrimps (Mysidacea), may be mentioned
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