438 On the Gastric Gland of Mollusca and Decapod Crustacea. 



When a solution of plant-chlorophyll in alcohol solution is com- 

 pared with a similar solution of enterochlorophyll by means of curves 

 obtained with the spectrophotometer, these curves do not correspond ; 

 but when we convert the plant-chlorophyll into the " modified " form, 

 or, what is the same thing, the slightly acid form, by means of acetic 

 acid, and allowing the solution to stand for a few hours, and then com- 

 pare the respective solutions, we find the maxima and minima of the 

 curves follow each other so closely as to lead one to conclude that the 

 pigments are closely related to each other. 



Again, if hydrochloric acid is added to a solution of plant chloro- 

 phyll in alcohol, and to a solution of enterochlorophyll in alcohol, and 

 these two solutions are examined by means of the spectrophotometer, 

 a remarkable agreement is noticed. 



The numbers taken for these measurements are the percentages of 

 the unabsorbed light, as the latter enable curves to be more easily con- 

 structed than by taking the co-efficients of extinction. 



I have also examined Lankester's " chsetopterin,"* and I find the 

 curve obtained by the spectrophotometer follows closely that of entero- 

 chlorophyll and that of modified chlorophyll. But chsetopterin is 

 soluble in glycerin, while enterochlorophyll is not. 



While examining Chcetopterus at the Plymouth Laboratory, I found 

 that an alcohol solution of the contents of the intestine, in the neigh- 

 bourhood of that part of the gut coloured by chaetopterin, gave exactly 

 the same spectrum as a similar solution of chaetopterin itself. The 

 discussion of the inferences to be drawn from this observation may, 

 however, be left for the present. 



I have seen enterochlorophyll present in a finely granular form in 

 the intestinal epithelium of Patella, and in the pseudo-villi of the 

 glandular stomach of the same mollusc one can see crowds of leuco- 

 cytes, some of which are insinuating themselves between the columnar 

 epithelial cells. The inference, of course, is that the leucocytes carry 

 away those substances which have been taken up by the epithelial 

 cells in a more or less digested condition. Some have supposed that 

 these granules are being excreted into the lumen of the gut, but in my 

 opinion, based upon a study of numerous sections of invertebrate 

 gastric glands, the excretion of enterochlorophyll by means of the 

 gland cells belonging to the various kinds mentioned takes place into 

 the lumen of the alveoli, acini, or tubes of tJie gastric gland, and from these 

 we can trace the excreted gland-cells into the intestine. 



From all these and other observations I have been forced, I must 

 confess against my inclination, to believe that enterochlorophyll is a 

 pigment which primarily has been taken up from the intestine dissolved 

 in a fatty medium, and is carried either by leucocytes, or in some 

 other \\ay to be deposited with this fat, and perhaps other reserve 

 * ( Quart. Journ. Micros. Sci.,' vol. 40, p. 447, &c. 



