Scientific J^/^otices. 383 



TO THE EDITOR OF THE ZOOLOGICAL JOURNAL. 



Sir, 



Finding in your last number for the current year, page 251, an allusion 

 to my discovery of the Metamorphosis in the Decapodous Crustacea, by 

 which I perceive that a degree of scepticism still exists, not only as to 

 the facts upon which it is based, but also as to the universality of metamor- 

 phosis in this tribe of animals, I have now to state what will I trust convince 

 you that if any delusion exists or source of error, it must rather attach 

 to M. Rathke than to me; not having seen his work I judge only from 

 the analysis with which you have favoured us in your interesting and 

 valuable Journal. 



First then, in regard to the Brachyura I have ascertained the newly 

 hatched animal to be a Zoe in the following Genera, viz. 1. Cancer. 

 2. Carcinus. 3. Portunus. 4. Eryphia. 5. Gegarcinus. 6. Thel- 

 phusa? 7. Pinnotheres. 8. Inachus. 



The Macrourous genera which I have actually ascertained to be likewise 

 subject to metamorphosis, are 1. Pagurus. 2. Porcellana. 3. Galathea. 

 4. Crangon. 5. Palaemon. 6. Homarus. 7. Astacus ! These embrace 

 all our most familiar native genera of the Decapoda. With regard to 

 Astacus however it will be necessary to be more particular. This genus 

 embraces but two species, the A. marinus or Lobster, and the A. fluviatilis 

 or River Crawfish ; now with regard to the marine species or Lobster I can 

 aver that it does actually undergo a metamorphosis, but less in degree 

 than any other of the above enumerated genera, and consisting in a change 

 from a cheliferous Schizopode to a Decapode; in its first stage being what 

 ^ would call a modified Zoe with a frontal spine, spatulate tail, and 

 wanting subabdominal fins, in short such an animal as would never be 

 considered what it really is, were it not obtained by hatching the spawn 

 of the Lobster. 



Are we then to consider the fresh water species of Astacus or Craw-fish 

 as an exception ? or is there not reason (from the above detail) to suspect 

 that this peculiarity may have escaped the notice of M. Rathke? If 

 however it should be found otherwise, it can only be regarded as one 

 solitari/ exception to the generality of metamorphosis, and will render 



