REPORT OF COMMISSIONERS OF IXLAND FISHERIES. 57 



habitat? 2. What is the distribution? 3. What is the economic 

 value of the species? 4. What is the season in Rhode Island? 

 5. When are the eggs laid, and how long after copulation? 6. How 

 long does the female carry the eggs? 7. What is the extent of the 

 hatching season? Some of these can be answered definitely, others 

 in a general way, while still others require further observation before 

 any answer can be given. The distribution given is from Rathbun 

 ('00); the common names and the notes on the habitats are from 

 "Fauna of New England," by M. J. Rathbun, and "Invertebrates of 

 Southern New England," by A^errill and Smith. 



Larval Forms. 



The crab, like the lobster and related forms, is hatched from the 

 egg in a form little resembling the adult. In its earlier stages, the 

 zoea, it is characterized by a well-developed abdomen and long dorsal 

 and rostral spines on the carapace. These stages, usually four or 

 five in number, in each of which one or more moults occur, occupy 

 a period probably of not more than one month. The next stage, the 

 megalops, shows many of the characteristics of the young crab. The 

 carapace becomes flattened, the spines are much modified — the dorsal 

 spine in many instances disappearing entirely — but the abdomen is 

 still extended. After several moults the megalops assumes a typical 

 crab form. 



The series of changes from the time of hatching to the young crab 

 are a subject of much interest and offer a wide field of investigation. 

 Many of the descriptions now available are incomplete, including 

 but one or two stages, usually the first zoea or the last zoea and the 

 megalops. This fact can be explained by the difficulty experienced 

 in keeping the young forms through the successive moults. One 

 can usually obtain a number of zoeae at the surface in a tow net 

 during the spring and summer. In this method, however, one is 

 never sure that the earliest stages are present. The most successful 

 method has been to raise the first stages from the egg and supplement 

 these with the forms taken in tow. 



