On the Development of the Crustacean Embryo. 177 



In thepinbrvos of otlior C'riistiiceii lln'aiif trior pairof loln'seiilarf^c 

 ill sizt' with little altfration of form, while flic |tostt'rior two j)airs 

 nro (h'velopctl into a|tpt'ii(lai,'fs that have hut a (lecidiious value, 

 since they never fullil the olliceof permanent orj^ans, and are gene- 

 rally east otY with an early moult. 



This is ohservahle within the ovum in Pulnuion, Cramjon, Sw., 

 and also in the marsupial embryo of Mi/gis after it has quitted the 

 ovum. 



The relation of tliese parts to the permanent organs the author 

 has closely traced, and kdieves that h(> has demonstrated that, the 

 three pairs of mobile appendages in the oirripedal or .WtxiiliKs form 

 of larva homologi/.e with the eyes and two pairs of antenna\ and 

 not with the antenna- and mandibles, as staled by Fritz Miiller, 

 Antou Dohrn, and others. 



The author, moreover, contends that the small pair oi fila- 

 mentary a|)i)eiidages seen on each side of the ocular spot, existing 

 in the yiotjtHi of C'irripedes. homologize with the peduncular ap- 

 pendage I'xisling in the lar\a of C((ll(/>i.'<, the arm-like appendages 

 in the pupa-stage of Cirripedes, the peduncle of the stalked C'irri- 

 pedes, and probably also with the long multiarticulate, antenna- 

 like organs belonging to the fossil Ptcn/i/otiis. 



lie also demonstrates the origin of the nerves in a mass of cellular 

 material that reaches from one extremity of the embryo to the 

 other. This divides into parts corresponding to the various somites 

 into which the animal divides. These masses gradually separate 

 from each other as the animal increases in size, and concentrate 

 into the several ganglia that form the great nervous chain. 



The author also show s the origin of the permanent organs of 

 vision, and the manner in which the luimber of lenses increases with 

 the growth of the aninial, and traces the origin of several of the 

 internal viscera and their mode of growth. 



He also figures, in minute detail, the larvie of the following 

 genera (those in italics are from British specimens, while aU the 

 others are from the collection sent to him by Mr. Power) : — 



Pal<pmon fluvialis, n. sp. 



sqttilht. Leach. 



Cranffon vulgaris, Loach. 

 Hymcnoccpa, Heller. 

 Alpheus obesimanus, Dana. 

 Hoinaralpheus, n. g. 

 Homarus inarinus. Leach, 

 Palinuriis vulgaris. 

 Asfat'UJi flu via til Li. 

 8quilln. 

 Poreellana rugosa. 



longicornis. 



Galatlica. 

 Pof/urus tibicen. 



elegans. 



Bernliardus. 



01ibinar\i» 

 Trichia. 

 Qelaaiiuus. 

 CyclograpKUs. 



Libinia. 

 Menivthiua. 

 Sfcnorhgnchus. 

 Mithrax. 

 Trapezia pectinata. 



ferruginea. 



Pihiinnus. 

 Melia tessellata. 

 Carpelodes rugipes. 

 Actinurus sctifcr. 

 Xantlio Lamarckii. 

 Actjra obesa. 

 Thia ? 

 Lionicra. 

 I'iriinela ? 

 Tlialainita. 

 AclielouB. 

 Kiiriptiia. 

 Thalassina. 

 Oarcinooystus, ii. g. 



