26S 



KNOWLEDGE. 



[December 1, 1900. 



morphosis drew their conclusions. The sea being 

 the natural and accustomed nursery of the lai-val fomis, 

 it has no doubt become expedient for some of the 

 colonists of land and fresh water to have young ones 

 which needed such a nursery as little as possible, and 

 which in some way got over their critical transfoniiations 

 while still in the ovum. The latter process must have 

 its merits, since it is adopted bv the prosperous order 



]£slheria packardi, Brady. Naniiliu*. 



of Amphipoda wherever they happen to be born, which 

 is generally in the sea. 



The rearing of entomostraca from dried mud has 

 enabled Professor Sars to trace very surely the develop- 

 ment of several interesting forms. His figures here re- 

 produced of the first larval form or Nauplius and the 

 fully-grown female of Esflieria packardi, Brady, from 



Esiheria jjickardi, Brady. FuUy-growu Female. 



Australia, are worth compai-ing with those of his own 

 Brarichipodopiis Jiodf/soiii from South Africa. The two 

 stages being the same, it will be easily seen how nearly 

 alike are the little nauplii, and how strangely 



Branchipodopsis hod(i^om. Sar.-. Ovigerous Fomalo. 



different are the adult females of these Phyllopoda. 

 The term nauplius. now so extensively applied in tiie 



class Crustacea, has itself an interesting history. It 

 was originally the name of a genus invented by the 

 illustrious O. F. Miiller for some tiny Copepoda. These 

 were really the young of Ci/rJii/m, and their larval char- 

 acter had been already pointed out by Leeuwenhoek 

 and de Geer. But they were so unlike their parents 

 that Miiller, so far from believing in any personal 

 identity of the young and adult fonns, would not allow 

 Ihem to belong to the same genus. It has been .ex- 

 plained on an earlier occasion how the connection of 

 the cirripedes with other groups of Crustacea was at 

 length established bv observation of the young, the 



Bi-anchipodopsis hodt/soni, Sars. Nauplius. 



parents having carried out such extensive and eccentric 

 transmutations that for ages they forfeited the honour 

 of belonging to the karkiuokosm. 



There is still one group of juvenile forms which must 

 not be passed over in silence. With it we may fitly 

 conclude our discursive story of the class Crustacea. 

 The group in question goes for the present under the 

 designation of PhyUosoma, a generic name meaning 

 leaf-body. But these laminar organisms doubtless 

 belong not to a single genus, but are the young of 

 many species distributed over several genera in more 

 than one family. They have even to our own day a 



X \ 



Phi/lJosoma laficorne. Leach. Giaut Scjllarid larva from New 

 Guinea, with limbs more than five inehes long. Reduced from 

 (iuerin's figure in the Crustacea of the voyage of '' La Coquille.' 



charm of mystery clinging around them, in that we do 

 not too well know their parents, only we know that 

 their parentage is noble. They are not the young of 

 insignificant creatures, but of macnirans built in the 

 grand style, the giant crawfishes and the mother-lobsters, 

 in other words, of the Paliuuridte and the Scyllaridie. 

 To be sure, in these at maturity, and in the latter 

 family especially, there is more size and substance than 

 attractive elegance of form. But the difference between 

 crabbed age and youth, acting as a fo'il, by contrast 

 serves to enhance the delicate bcautv of the Phvllo- 

 soma. Although not gorgeous in colouring, and uot 



