Nauplius Stage of Prawns. 83 



It appears scarcely desirable that any classification of a 

 general character should be attempted upon larvfe that have 

 been so imperfectly made known as that of Oalathea. And, 

 further, it appears to me that we have the forms of many types 

 yet to determine before we dare hope to establish any per- 

 manent classification based on our knowledge of develop- 

 ment. 



Even so small a generalization as that which Claus has 

 made, that the development of the cephalon and the pleon, with 

 their respective appendages, anticipates that of the pereion 

 with its limbs, is upset in the development of the common 

 lobster, where the pereion and all the pereiopoda are well 

 formed before a single appendage belonging to the pleon is 

 seen. This is shown in the figure of the larva of Homarus 

 ■which accompanied my paper read at the Royal Society in 

 March 1876, as well as by the researches of Erdl, 1843, and the 

 excellent memoir and illustrations of Mr. Sydney F. Smith 

 on the American lobster [Homarus americanus^ Edw.), 1872, 

 Amer. Journ. Sci. 



To return to the Nauplius, Fritz Mliller says, " The child 

 must surely have a father." True ; but let it be the legitimate 

 one. The young of Penceus is not known. It appears to me 

 rather remarkable that, among the numerous specimens of 

 several species that have been brought home in the * Chal- 

 lenger,' I have not been able to find one with ova attached. 



There are conditions in some of the Peneids which show a 

 variation in the structure of the reproductive apparatus from 

 that of the more-known prawns that is suggestive of diiferent 

 habits ; and I stoutly maintain that it is the duty of every era- 

 bryologist, and of Fritz Miiller in particular, to determine the 

 larva of Penceus before we can assert that the young of this 

 genus or any of the prawn-groups can be said to be known to 

 pass through a Nauplius-iovm. 



Fritz Miiller says that it cannot be the young of a Cirri- 

 pede or rhizocephalous Crustacean. He bases this opinion on 

 the formation of the heart, liver, and mandibles. All observa- 

 tion strongly supports the conclusion, arrived at long since by 

 Milne-Edwards, that the structural detail of animals in their 

 earliest stages corresponds more with their order than in their 

 generic features. What do we know of the development of 

 the Rhizocephala ? What do we know of the development of 

 Sacculina, Cletstosoma, Peltogasfer, or any of the parasitic Suc- 

 toria? or as to what changes these undergo after the NaupUus- 

 stage before they attach themselves as parasites to other Crus- 

 tacea? 



Dr. Power has shown us that in one of these [Carcino- 



6* 



