490 Mr. A. T. Masteriium on the Nutritive and 



organisms react towards carmine particles in tlie same way as 

 they do towards undoubted foods. It is evident that this is 

 all we require to assume for our purpose, without discussing 

 the point as to whether a sponge, for example, can be kept 

 alive for an indefinite period by feeding it upon carmine 

 exclusively. 



The second objection which might be urged is that the 

 choanocytes were overfed, and that therefore the phenomena 

 above described are of a pathological nature. 



In this connexion Hteckel (6) has observed that in many 

 calcareous sponges he found specimens in which the flagella 

 had atrophied and the flagellated cells had assumed the 

 amoeboid state. 



Metschnikoti' (10) finds and describes allied phenomena in 

 Ascetta chit/irus, and he also notes that feeding with an excess 

 of carmine causes obliteration of the chambers in Halisarca 

 pontica, the whole interior of the colony being reduced to an 

 amoeboid mass. 



Carter (2), Lieberkiihn (8), and others give instances of the 

 same kind. 



Sedgwick (13), after quoting some of these instances, re- 

 marks : — " The collared cells are thus inconstant, and appear 

 to be merely parenchyma-cells specially modified under 

 certain conditions and cajiable of passing back into their 

 original form Avlien the need for them has passed away." 



Sollas (14) mentions an appearance like that of a collared 

 cell budding off an amoeboid cell into the mesoderm. 



Bidder (1) states that in Ascetta the collared cells wander 

 through the ectoderm and, becoming perforated, form a pore; 

 and there are numerous other cases in the development of 

 sponges which show that the collared cells arise from amoeboid 

 and are readily transferred into either stage. The apical 

 growth of sponge-colonies probably proceeds on the same 

 lines. 



All the cases above cited, in whicli the transformation of 

 collared cells is effected in the adult sponge, are usually re- 

 garded as pathological, and so they ])robablv are in the sense 

 that they are the result of normal processes driven to an 

 extreme ; and it does not follow that all transformation of the 

 collared cells upon feeding must necessarily be pathological. 



In these experiments care was taken to avoid as far as 

 possible all unnatural factors. Freshly obtained apparently 

 liealthy colonies were used, and attemjits were made to avoid 

 an excess of carmine either as to quantity or size of the 

 particles. There is also no ap])earance in the sections which 

 would point to overfeeding, all the collared cells being uni- 



