178 Capt. DuCane on the Metamorphosis of Crustacea. 



or ameliorator, the trees remaining to defray the expense and 

 loss of time. The prejudice of the damage done to trees by 

 sheep is groundless, compared to the benefit to be derived 

 from their use as here recommended ; and we are quite sure 

 that it could be acted on with the greatest benefit to the land 

 and to that of the vicinity by the shelter afforded, and that 

 the value of every estate, large or small, would be very much 

 increased by the general adoption of such a plan. 



S. E. Cook. 



Carlton, 16th August. 



XX. — Letter from Captain DuCane, R.N., to the Rev. 

 Leonard Jenyns, on the subject of the Metamorphosis of 

 Crustacea*. With Plates VI. and VII. 



Southampton, August 20, 1838. 



Sir, 

 The British Association for the Advancement of Science 

 having requested me to present a report at its Meeting at 

 Newcastle this year on the subject of the metamorphoses of 

 the Crustacea in the Southampton waters, I beg to trouble 

 you with the following observations relative to the metamor- 

 phoses of the ditch prawn {Palcemon variabilis) and common 

 shrimp (Crangon vulgaris), which I shall be obliged by your 

 laying before the Association. 



I last year, through Mr. MacLeay, presented drawings of 

 the larva of the ditch prawn, exhibiting the appearance it pre- 

 sented from the time of its first exclusion from the egg till 

 the end of the third day, when my specimens died. I have not 

 this year been able again to obtain the larva of the prawn di- 

 rect from the egg ; but the ditch which is the locality of this 

 particular species, having supplied me with the larva in great 

 abundance, I have been enabled very satisfactorily to trace the 

 various changes it is subject to in the progress towards its 

 adult state. 



These changes, as shown in the accompanying drawings, 

 are four in number ; the three last may however, I think, rather 

 be considered as a gradual and progressive development 



* This important letter arrived at Newcastle too late to be read at the 

 Section of Zoology and Botany. — Edit. 



