STUDIES ON LARVAE OF CRABS OF THE FAMILY 

 PINNOTHERIDAE. 



By O. W. Hyman, 



Of the College of Medicine, University of Tennessee. 



The material on whicli the origmal portion of this paper is based 

 has been collected at Beaufort, North Carolina, during several 

 summers. 



All of the first zoeal stages originally described in this paper have 

 been obtained by hatching them in the laboratory. Ovigerous 

 females were collected and, if the form was abundant, those whose 

 eggs were in an advanced stage of development selected. The stage 

 of development may be determined readily by observing the depth 

 of color of the yolk mass. In newly laid eggs the yolk is deeply 

 colored and it becomes progressively lighter as the embryos develop. 

 When the females have been selected they are placed in finger bowls 

 filled with sea water. It is best to place not more than three females 

 tosether and to have a bit of shell in each bowl. The crabs are less 

 excited when they can hide. The eggs hatch at nightfall and the 

 zoeas will live for about a week if the water is changed daily and the 

 bowl kept in a cool place. 



The second zoeal forms have been secured by collecting large num- 

 bers of the first zoeas from the tow and keeping them m finger bowls 

 until a few have molted. 



The writer wishes to express his appreciation of the courtesies 

 extended to him by the Bureau of Fisheries and especially by Charles 

 Hatsel, the acting director of the station. I also acknowledge with 

 gratitude the assistance that has been given me unfailingly by Dr. 

 Waldo L. Schmitt and Miss Mary J. Rathbun, of the United States 

 National Museum. 



THE PINNOTHERID ZOEA. 



The zoeas of the Pinnotheridae do not form a well-defined, homo- 

 geneous group as in some other families. The only feature that is 

 common to them all and serves to distinguish them from the zoeas 

 of other families, is the minute size of the antenna. This is so small 

 in Pinnotheres ostreum that it hardly can be discovered and is only 

 0.2 mm. long and quite slender in P. maculatus in which it is largest. 



In other families the arrangement and size of the spines of the cara- 

 pace form distinguishing features of the zoeas. Among the Pinno- 

 therids there is no uniformity in this respect. In P. liolothuriae there 

 is not a vestige of any of the carapace spines (fig. 48) while in Disso- 



No. 2497.— Proceedings U. S. National Museum. Vol. 64. Art. 7. 



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