EEPOKT ON THE AMPHIPODA. 503 



concealed beneath the preceding segment. The telescoping of these two segments is 

 facilitated by the depression, and is of obvious importance for the bending and unbending 

 of the pleon. 



1879. Weze^niowski, August. 



Vorliiufige Mittheilungen iiber einige Amj)hipocIen. Beitrage zur Anatomie cler 

 Amphipoclen. Zoologischer Anzeiger. II. Jahrgang. 1879. pp. 447-450, 465- 

 469, 487-491, 511-515, 536-540, 564-569. 



Also in a Separat-Abdruck, 24 pp. 



These valuable contributions to the anatomy of the Amphipoda are based chiefly on Gophma 

 polonka, Pallasea cancelhcs, Callisoina hranickii, and two varieties of Gammarus pulex. 

 The matrix or hypodermis is shown to be completely distinct from the adipose tissue, the 

 former, as examined' in PaUasea canceUug, presenting a typical stratified cylindrical 

 epithelium, having its small granular cells provided each with a nucleus and nucleolus, the 

 latter consisting of relatively large, rounded and somewhat angular, very pale cells connected 

 together without intercelhilar substance. This latter forms a sheath for the alimentary canal, 

 and fills the space between it and the heart, for which it forms the serous covering, inter- 

 cellular substance here making its appearance. By flat or string-like offshoots it connects 

 the various internal organs with one another and with the external covering of the body. 

 On various parts of the inner surface of the matrix it forms a layer of connective tissue to 

 which the ofishoots above-mentioned are fastened. The fat-drops, which are met with 

 most constantly between the alimentary canal and the heart, are rare or almost entirely 

 wanting in fasting Amphipods, but abundant in well-fed specimens. 



The muscular system in Gopilana p)olonica is thus described. The flexors of the back present 

 two separate systems. The one consists of oblique muscles running from above and behind 

 obliquely forwards and downwards. Each muscle begins halfway up the segment and 

 inserts its lower end on the ventral surface of the preceding segment. These are wanting 

 in the four first segments of the body, but present from the fifth to the tenth, the three 

 following segments, which in Goplana polonica are coalesced, possessing a common very 

 strong oblique flexor. The other set of flexors is thus constituted. On either side in the 

 lower part of the segments run, from one segment to the next, and interlaced, pairs of 

 muscles parallel to the ventral surface of the body. These muscles are united at the places 

 of insertion, so that they form elongated links. These "Wrzesniowski calls longitudinal 

 flexors of the back. The regular arrangement of these prevails from the fourth to the ninth 

 segment of the body. Oidy the upper muscle enters the tenth segment. The three 

 coalesced segments have a single very long longitudinal flexor, In the front part of the 

 body these muscles run without interruption from the hinder rim of the head to unite at a 

 common place of attachment in the fourth segment of the body. 



The extensors, which are considerably stronger than the flexors, form strong tracts on either side, 

 extended between the front rims of neighbouring segments. The front divisions of the 

 extensors and flexors raise and lower the head. 



The abdominal feet are moved by a complicated system of muscles. The first basal joint of 

 each foot possesses an extensor and a flexor, which draw the whole foot forwards and 

 backwards. The two terminal branches of the foot have each a very thin and broad 

 extensor and flexor, running from the upper rim of the basal joint to the commencement 

 of the corresponding branch. Each branch has its own abductors and adductors, the outer 



