On tJie Development of the Crustacean Emhryo. 177 



In the embryos of other Crustacea the anterior pair of lobes eularge 

 in size with little alteration of form, while the posterior two pairs 

 are developed into appendages that have but a deciduous value, 

 since they never fulfil the office of permanent organs, and are gene- 

 rally cast off with an early moult. 



This is observable within the ovum in Palcemon, Crangon, &c., 

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

 ovum. 



The relation of these parts to the permanent organs the author 

 has closely traced, and believes that he has demonstrated that the 

 three pairs of mobile appendages in the cirripedal or Nauplius form 

 of larva homologize with the eyes and two pairs of antennse, and 

 not with the antennte and mandibles, as stated by Fritz Midler, 

 Anton Dohrn, and others. 



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

 mentary appendages seen on each side of the ocular spot, existing 

 in the Nauplii of Cirripedes, homologize with the peduncular ap- 

 pendage existing in the larva of Caligus, the arm-like appendages 

 in the pupa-stage of Cirripedes, the peduncle of the stalked Cirri- 

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

 like organs belonging to the fossil Fterygotus. 



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

 material that reaches from oue 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 shows the origin of the permanent organs of 

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

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

 internal viscera and their mode of growth. 



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

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

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



Falamon fluvialis, n. sp. 



sqidlla, Leach. 



Crangon vulgaris, Leach. 

 Hymenocera, Heller. 

 Alpheus obesimanus, Dana, 

 Homaralpbeus, n. g. 

 Homarus marinus, Leach. 

 Palinurus vulgaris. 

 Asfacus fliiviatilis. 

 SquilJa. 

 Porcellana rugosa. 



longicornis. 



Galathea. 

 Pagurits tibicen. 



elegans. 



BernharduB. 



Olibinarus. 



Libinia. 

 Menistbius. 

 UtenorhyncJms. 

 Mitbrax. 

 Trapezia pectin ata. 



ferruginea. 



Pihimnus. 

 Melia tessellata. 

 Carpelodes rugipes. 

 Actinurus setifer. 

 Xantho Lamarckii. 

 Actjea obesa. 

 Thia ? 

 Liomera. 

 Pirimela ? 

 Thalamita. 

 AcheIou8. 



Trichia. Euriphia. 



GelasimuB. ] Thalassina. 



Cyclograpsus. ' Oarcinocystus, n. g. 



