LIFE HISTORY OF THE COMMON SHRIMP 
15 
fluctuations begin and only end with disappearance of the adults from the fishing. 
The rise in proportion of the females succeeded by a fall appear to be the result of 
differential behavior of males and females associated with spawning. We have found 
no indication of a sex reversal in Penaeus such as has been claimed by Berkeley for 
Pandalus. 
Further data is being collected on this interesting question. 
Figure 9.— Percent of females appearing in catches from inside and outside waters of Georgia from February 1, 1931, to August 
15, 1932, during which period 58,521 shrimp were measured and examined. 
LARVAE 
The study of the larvae of Penaeus by Muller (1863, 1864), Brooks (1883), and 
Kishinouye (1900b) have shown the main features of the unusual larval history be- 
ginning with the nauplius, not found elsewhere among the higher Crustacea. There 
are a large number of stages (6 to 8) including nauplius, metanauplius, protozoea, zoea, 
metazoea, and mysis. In no case has the species of the larvae been known with cer- 
tainty, and in consequence there exists no data for the identification of the larvae. 
This is a serious lack where 4 species of penaeids appear in the commercial catch and 
15 or 20 have been recorded, the larvae of which may be encountered. Other facts 
indispensable to this phase of the life history, such as the duration of the stages and 
their behavior, are also lacking. 
The extensive plankton collections of the investigation have not yet been studied 
in detail, and although larvae are present we are as yet unable to give a satisfactory 
summary of their distribution. 
YOUNG 
From the distribution of the mature adults, spawning must take place predomi- 
nantly, if not exclusively, in outside waters of high salinity. What little is known of 
the distribution of the larvae does not conflict with this. The distribution of the post- 
larval young is, however, different. These forms, essentially similar to the adult 
except in size, the smallest that we have obtained measuring 7 mm in length, give up 
the swimming habitat of the larvae and seek the bottom, thus resembling the adult in 
habits as in form. The young, as has been stated, are found on muddy bottoms in 
shallow water of high temperature and low salinity exclusively in bays or inside 
waters and often far from the ocean or Gulf. The upper limit of size of the young in 
