REPORT ON THE AMPHIPODA. 597 



The introduction, pages 3 to 29, comprises eight sections, as follows : — 



1. Allgemeine Charaktere. Among these are noted the very striking differences presented by 

 the antennas in the two sexes, the absence of palp-appendages fi'om the maxillae as well as 

 the maxillipeds, and the limitation of the triarticulate mandibular palp to the male sex. 



H. Aeussere Erscheinung und Korperform. Claus knows of no instance in this group in which 

 the epimera or side-plates are absorbed in the segment as in the Phroiiima-gToup. The 

 fifth and sixth pleon-segnients are always coalesced, and sometimes the telson is united to 

 them without suture. 



3. Gliedmassen. The upper or front antenna; never have an accessory flagellum ; observers 



have been misled by the produced peduncle in Phorcus to regard the principal flagellum 

 as accessory. The second or hinder antennae have the peduncle and flagellum not sharply 

 defined the one from the other. In almost all cases the first or coxal joint is absorbed into 

 the integument of the head. Claus notices that there are fine setse along all the joints 

 except the first of the folding antennas of the male, but of their function he is not quite 

 certain. The left mandible has a tooth-like process of considerable size, which is either 

 absent or as a rule very weakly indicated on the right mandible. The first joint of the 

 mandibular palp, which is generally small in the Gammarina, is generally large, and 

 sometimes enormous, in the Platyscelidae. For the terminal part of the gnathopods various 

 expressions are used, Greifhand (Zange) for a subchelate, Scheere for a chelate, hand and 

 finger, doppelie Scheere when the chelate hand and finger are applied against an immov- 

 able process of the wrist, and ziisammengasetde Scheere when the chela is formed by a 

 simple hand and finger applied against the process of the wrist. The marsupial plates of 

 the female are generally lanceolate, yet widening at the free end, and occasionally so much 

 so as to be like a stalked leaf. 



4. Integument und Hautdrlisen. 



5. Nervensystem und Sinnesorgane. The ganglia of the first two peraeon-segments are 



drawn together and taken up into the group of the suboesophageal ganglion. The last 

 peraeon-ganglion is relatively small and united with the preceding, while the fourth pleDn- 

 ganglion, which provides for the hinder section of the pleon and in the Gammarina remains 

 separate, is much reduced, united with the third ganglion, and placed in the third pleon- 

 segment. In the more elongate species lateral nerves issue not only from the ganglion- 

 masses, but also from the longitudinal commissures in the person-part of the ganglionic 

 chain. In the genera Eutyphis, Thamijris, Simorhynchus, and the Oxycephalidse there are 

 centrally from the origin of the great front antennary nerves two short nerves, each of 

 which provides for a sense-organ lying just in front of the brain, which is evidently an 

 organ of hearing. The contents of the vesicle in question are a clear watery fluid and 

 what is obviously an otolith. 



Of the eyes Claus says : — " Eine Facettenbildung der Cuticularbekloidung habe ich in keinem 

 Falle beobachtet, vielmehr bildet, wie bei Phronima, die zarte durchsichtige Korperdecke 

 iiber dem Auge eine gleichmaissige Cornea. Immerhin tritt bei tiefer Einstellung eine 

 sechsseitige facetteniihnliche Felderung hervor, bedingt durch den optischen Querschnitt 

 der paarigen Krystallkegelzellen, deren zwei grosse Kerne erhalten bleiben. Oberhalb der 

 Krystallkegelzellen breitet sich eine deutlich nachweisbare Hypodermis als Matrix der 

 Cornea aus, welche der schon von Claparede vertretenen und von (irenacher aufrecht 

 erhaltenen Auflfassung entgegensteht, nach welcher iiberaU die BildungzeUen der Krystall- 

 kegel (mit den Semper'schen Kernen) zugleich die MatrixzeUen der Chitinhaut seien." 



On the iSpiirfiiden or Riechhaare he says that here and there the end is open in consequence of 

 the breaking oif of the point, and that this may have led to the erroneous view " als 

 besiissen die Riechhaare an der Spitze Oeffnungen." For the latter view see Note on 

 Leydig, 1878, with whom Hoek, 1879, agrees. 



