61 



the centre (fig. 50, AL") ; their protoplasm has practically 

 disappeared, there are just a few strands left crossing the 

 cells which contain the green pigment granules clustered 

 together in little groups. The connective tissue membrane 

 bounding the alveolus has here become verv thin, and the 

 circular muscles have practically disappeared. MacMunn 

 (21) has termed the green pigment enterochlorophyll, and 

 finds that the spectrum given by the spectrophotometer 

 is almost exactly that of plant chlorophyll modified by the 

 addition of a little acetic acid acting for several hours. 

 He considers, therefore, the pigment to be modihed 

 chlorophyll. Miss Xewbigin considers the resemblance 

 of this pigment to chlorophyll to be only superficial, and 

 places it in the same category as Chaetopterin and 

 Bonellin. 



It is, however, almost certain that the colour of 

 the digestive gland at an}- time is dependent on the colour 

 of the food, and several observers, including List and 

 Dastre and Floresco (6 and 19), have shown that if 

 Lamellibranchs are fed with colouring matter this appears 

 in the form of small granules in the cells of the digestive 

 gland, and even after two hours can be traced there. List 

 shows, further, that it is a direct absorption, and not a 

 function of the wandering cells. 



In order to determine the action of the secretion of 

 the digestive gland, the following bio-chemical experi- 

 ments Avere undertaken. They confirm those of Roaf (22) 

 on the glands in other molluscs. 



The glands were taken from several Pecten, the 

 whole mass weighed and then minced up in a dehnite 

 volume of distilled water to which a little HC^N" (or toluol 

 when testing for sugar) was added as a preservative. This 

 was allowed to stand for twenty-four hours and then 

 straiued through muslin and a series of solutions made 



