Zoological Society bulletin . rofessorE. A. Andrews,* of Johns Hopkins University. It has long been known that the crayfisheshave no larval surface-swimming stages as dotheir marine relatives, the lobsters and early as 1755 von Rosenhof noticed that theyoung of the European crayfish are similar tothe mother and that they remain with her fora time after hatching. Rathke in 1829 showedthat the young emerges from the egg in essen-tially the adult form and so has no metamor-phosis. Later, however, Huxley (1879) provedthat the young before the first moult are not ex-actly similar to the a
Zoological Society bulletin . rofessorE. A. Andrews,* of Johns Hopkins University. It has long been known that the crayfisheshave no larval surface-swimming stages as dotheir marine relatives, the lobsters and early as 1755 von Rosenhof noticed that theyoung of the European crayfish are similar tothe mother and that they remain with her fora time after hatching. Rathke in 1829 showedthat the young emerges from the egg in essen-tially the adult form and so has no metamor-phosis. Later, however, Huxley (1879) provedthat the young before the first moult are not ex-actly similar to the adult, but differ in the lackof setae, or bristles, and in the form of thefirst and sixth abdominal appendages. Thusit will be seen that there is only a slight degreeof metamorphosis and of a different sort fromthat seen in the marine Crustacea. The reason for the elimination of the free-swimming stages is probably to be found in theiradaptation to a special habitat. If a surface-swimming stage were present, as in the lobster,. A FEMALE CRAYFISH Showing method of carrying the by R. C, Osburn. the young of the mountain stream species mightlie carried into the larger streams, while thoseof the inhabitants of the lowland streams mighteven be carried out to sea at this period. The eggs of the crayfishes are regularry laidin the early spring and the time of laying for *The Young of the Crayfish, Astacus and Cam-barus. Smithsonian Contributions to Knowledge, pp. 1-79, plates I-X. ZOOLOGICAL SOCIETY BULLETIN. 927 any species may extend over a considerableperiod—in Cambarus bartoni, for example, fromMarch loth to May 15th. Chidester* has ob-served that in C. bartoni var. bartoni there isalso an autumnal spawning season beginningwith the latter part of Sejjtember and extendingthrough October and November. Although Chi-dester does not discuss the matter, this probablydoes not mean that two broods are produced ina season, but that some of the females maturetheir
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