NOTES AND MEMORANDA. 461 



bitint^ hairs. The maxillipeds were well developed, each having a 

 lai-ge exopodite, used in swimming ; while the five thoracic legs 

 existed as mere buds, the first four being already bifid, but remain- 

 ing folded beneath the thorax. 



The larvEe moulted three or four times before attaining a proper 

 " mysis " condition. After attaining this condition they were 

 accidentally killed. They fed freely from a few hours after hatching 

 during their whole lives. 



The eggs from the abdomen of the mother measured rather less 

 than 1 mm. in long diameter, and each female carried about 150. 



The only difference between the larva here described and that 

 shown by Boas to be characteristic of the northern salt-water form 

 of Palsemonetes lies in the occasional presence, in the Plymouth 

 larva, of the single rostral spine ; and the facts above mentioned 

 as to the variability of the adult rostrum may perhaps be considered 

 to deprive this single difference of any great importance. 



We have, therefore, in Plymouth a race of PaJsemonetes which, 

 while approximating in its habits to the races of Southern Europe, 

 retains, in its development at least, a complete resemblance to those 

 northern forms from which it is probably descended. 



W. P. R. Weldon. 



