SOME BRACKISH-WATER AMPHIPODA. 659 



" Altona. Ponton. 9.vii.00." 107 specimens, all rather small, 

 averaging 8-9 mm. in length; the eyes in these have recldish- 

 brown pigment. 



"Altona. Due d'Alben. 1.x. 00." 1 specimen, a female. 



All these belong indubitably to the brackish-water type. The 

 very young animals differ slightly from the adult, the eyes are 

 round, the peduncles of the antennse are about equal in length, 

 the pleon clusters are represented each by a single spine, and the 

 i-ami of the third uropod are much more unequal than in the 

 adult. Some of the specimens, especially those from Blankanese, 

 are more setose than the others. 



" Hamburg." The " Fleet " referred to is one of the canals 

 which run through the inner town. These canals are mostly 

 dependent on the tide, with mud-banks exposed at low tide. 

 " Grasbrokhafen" and " Indiahafen " are blind alleys as it were 

 opening out of the Harbour basin ; they are deep and broad, the 

 bottom consisting of clay, sand and mud, with organic detritus 

 deposits providing food for a rich animal life. 



" Fleet 1. Grund. 25.vi.00." 1 specimen, a male 11 mm. 



" Fleet 1. Krotzprobe. 23.vii.00." 1 specimen, a male, with 

 exceptionally large eyes. 



" Grasbrookhafen. Grund. 19.xi.00." 2 specimens 19-20 mm. 



" Grasbrookhafen. Due d'Alben. 20.vi.00." 18 specimens 

 mostly small, the largest 9-10 mm. 



" Indiahafen. Ponton. Oberflache. 22.V.00." 77 specimens, all 

 very young. 



The specimens from the " Fleet " samples show intermediate 

 characters, forming the link between the two extremes of the 

 species. They are more solid in appearance than the brackish- 

 water form, but the chitin is not as thick as in the freshwater 

 animal. The spines and long hairs vary greatly in number, and 

 the narrowing of the basal joints of the hinder pereeopods also 

 appears variable. Of the " Grasbrookhafen " specimens the two 

 from the bottom are typical freshwater ones ; the eighteen spe- 

 cimens from the " Due d'Alben " (piles driven in and used for 

 making ships fast) are all delicate in appearance, the largest 

 showing intermediate characters. Some of the small ones, 3-4 mm . 

 long, are extremely slender and compressed, almost thi-ead-like, 

 and with very few hairs. The " Indiahafen " specimens are all 

 very small, the brackish-water form. 



" Alte Dove Elbe and Moorflether Concave." Volk says of 

 these that, taken together, they form a qviiet bay with the bio- 

 logical characters of a backwater (" Altwasser "), but influenced 

 to some degree by the tide. These samples are the most interest- 

 ing of the series ; in some both the fresh- and the brackish- water 

 forms occur together, with the "intermediate " form. 



" Moorflether Concave. Grund I. 23.vii.00." 1 specimen, a 

 female 9 mm., with the delicate appearance of the brackish-water 

 form, but with dense clusters of long hairs on antennse, perteo- 

 pods, and telson. 



