GIGANTOCYPRIS MULLERI 239 



1 



The lacunae of the labyrinth can be seen to contain considerable numbers of blood 

 cells. Blood cells, while they are circulating, have the normal appearance of approxi- 

 mately spherical bodies. They usually contain a group of vacuoles at one side of the 

 nucleus and often a small pseudopodium. Where they adhere to connective tissue fibrils 

 this pseudopodium may become very prominent. In the labyrinth, however, the pseudo- 

 podium takes on remarkable shapes. All stages can be found from a normal cell, through 

 forms in which the pseudopodium has extended out into a filiform structure, to cells 

 showing a complicated branching system of outgrowths. These outgrowths may have 

 enlargements at the end and it is by these that the cell is moored to the wall of the 

 lacuna. Where the pseudopodia end in a branching system (Fig. 176) I deduce that 

 these are still growing outwards and have not yet made contact with the labyrinth wall. 



There is a peculiar tissue, which I have called nephrocyte tissue, situated just below 

 the lateral parts of the adductor muscle. From its proximity to the maxillary segment 

 and from its appearance in sections (Plate XLI, fig. 7) I thought at first that it represented 

 a maxillary gland. However, the apparent end sac which is so obvious in the photograph 

 is not, in fact, a sac as its cavity is completely open posteriorly. The walls are made 

 up of enormous stellate branching cells, some of which project from the surface and 

 ramify particularly anteriorly. One of these can be seen very clearly projecting down- 

 wards in the photograph. Its nucleus can also be seen, and this is typical of the tissue. 

 The nuclei are very swollen and appear to consist of an irregular inner staining mass 

 surrounded by a clear space. They have all the appearance of degenerating nuclei, but 

 this seems improbable as they all appear to be in the same stage. The cytoplasm stains 

 markedly with chlorazol black and is uniformly vacuolated throughout. The vacuoles 

 all appear to be of approximately the same size and project from the surface so that 

 the latter has a very marked warty appearance. 



In referring to this tissue as nephrocyte tissue I do not imply that there is any 

 evidence that it is excretory in function, but merely that in a morphological sense it 

 compares with the nephrocytes of other forms. These are usually associated with peri- 

 cardium or else, as in Isopods, with the gills. In Gigantocypris the nephrocyte tissue 

 occurs in the upper end of the maxillule where there is a globular appendage (Figs. 1 , 3 

 and Plate XLI, fig. 5) which I consider a gill. It resembles the typical Branchiopod gill 

 and is situated in the position where one could expect to find a gill. It also occurs in 

 Doloria (Fig. 1) but here it is much more flat and is inconspicuous. It probably repre- 

 sents the missing epipodite of the maxillule. Hansen (1925, p. 68) said that he thought 

 that a very thick plumose seta was a rudiment of the epipod. However, the gill that 

 I describe here is so thin walled that in potash preparations such as Hansen used it 

 would have been extremely difficult to make out with any certainty. 



