228 G. M. Giles — Notes on the Amphipoda of Indian Waters. [No. 3, 



ganglion masses, the ventral ganglia included, is surrounded more or less 

 completely by a layer of small round cells that have all the histological 

 characteristics of leucocytes. From an examination of certain figures 

 illustrative of current researches in the group, I am inclined to think 

 that these have been, in some cases, mistaken for nervous elements and 

 described as portions of the ganglion system. They are, however, simple 

 granular rounded cells vt^ith small indistinct nuclei, both cell substance 

 and nuclei greedily absorbing all dye stuffs. These cells are quite 

 without tails or other protoplasmic connections, and appear to be packed 

 in the intercellular lymph tissues surrounding the ganglia rather than 

 embedded in any intercellular material. They are certainly mesoblas- 

 tic and probably are plasmic cells whose function it is to subserve the 

 rapid nutritive changes going on within the ganglionic system. 



Muscular System. — This, in one species, is but feebly developed, the 

 sections contrasting strongly with those of species of more active habits, 

 such as inhabit the surface. In the head a number of radially placed 

 bands suspend the gizzard, those in the middle line above being the 

 m.ost strongly marked. A strong band runs between the anterior part 

 of the under surface of the gizzard obliquely downwards and backwards 

 to the antero-inferior corner of the " sifting " stomach. The body mus- 

 cles are especially feeble, the best developed being the great extensors of 

 the segments, which attain a development somewhat superior to the 

 other body muscles. The great obliquely vertical bands which take up 

 so large a share of the segmental space in most crustaceans are scarcely 

 developed at all in the thoracic segments and but feebly so for even the 

 first three abdominal segments, which usually have these muscles of 

 immense size for keeping up the constant vibrations of the three anterior 

 abdominal appendages. Living, however, as this species does, imbedded 

 in tolerably thick mud, it can have but few opportunities for putting 

 this movement in action, the want of a free current through its branchial 

 plates being met in another way. The muscles of the thoracic appen- 

 dages and of the last three abdominal appendages are correspondingly 

 weak, the greater part of the space within the articulations being taken 

 up with aggregations of plasmic cells like those already described 

 as surrounding the ganglionic centres. 



Digestive System. — The gnathites, already described, work beneath 

 a vaulted space formed by the sterna of the cephalic and maxillipedal 

 segments. From the middle of this vault a funnel-shaped jjharynx leads 

 into a very narrow oesophagus of some length, which opens into a large 

 cavity which appears to function as a gizzard. This cavity is nearly 

 rounded in ti^nsverse section, but slightly flattened from above down- 

 wards, especially behind, the width of the lumen being about one quarter 



