244 JA.MKS KRNEST KIXDRED. 



follows that in the Asteroidea, Ophiuroidea, Echinoidea and 

 Holothuroidca with tests (e.g., Psolns), which live in regions of 

 high free oxygen content, due to tidal currents, there is 

 enough oxygen in suspension in the perivisceral fluid for ordinary 

 metabolic activity. Therefore in these forms no oxygen-carrying 

 cells are developed and the cellular modifications which occur in 

 the cells of the perivisceral fluid may be regarded as independent 

 of the relations of the breathing organs. Further we would 

 expect to find efficient oxygen-carrying cells in the Holothuroidea 

 which have a relatively high development of muscle, for the 

 needs of which the free oxygen content of the perivisceral fluid 

 is not sufficient. The hemocytes are the cells which fulfill this 

 requirement in the Holothuroidea and will be discussed later. 



If the "amcebocytes with red spherules" are not to be regarded 

 as oxygen-carrying cells, are they then related to the transfer and 

 storage of food as suggested by Cuenot? As a partial answer to 

 this query are the results and conclusions of Awerinzew ('n) 

 who carried on investigations on the habitat and food relations 

 of two varieties of S. drobachiensis . Awerinzew observed that 

 the two colored varieties of this species lived in different types of 

 environment, the green-yellow forms living on a mud and stone 

 bottom and the red forms amongst red algae. He assumed that 

 the pigment in the food of the red forms was carried from the 

 intestine to the skin and deposited there. The pigment in the 

 prrivisceral cells would then be due to the food eaten. He 

 checked his results by injecting carmine particles in solution into 

 the alimentary tract and found that these particles were carried 

 to the skin, but the distinctions between the types of cells en- 

 gaged in this activity were not made clear, so that it is possible 

 that the cells were leucocytes carrying on their normal activity as 

 phagocytes and there is no case for the pigmented cell- as food 

 carriers . 



The "amcebocytes with red spheruk-s" are far more numerous 

 and larger in the perivisceral fluid of S. fraud scan us th.m thry are 

 in S. drobachiensis. This fact leads to the suggestion that the 

 color of the body wall is due to a difference in numbers of the red 

 cells in the two species. 



Since it has not been proven that tin- " amoebocy tes with red 

 spherules" are developed from other cells by the ingestion of 



