Pseudochlorophyll-corpuscles in Tridacna. 447 



tical with the above-mentioned granulations, I do not know ; 

 but at any rate it may be regarded as certain that the cell- 

 contents contain starch. 



The seat of the green cells is not determinable at the first 

 glance. It is indeed quite clear that they never occur intra- 

 cellularly, like the yellow cells of the Actiniee for example. 

 For this indeed the tissues of the Mollusca are much too small- 

 celled. But whether they are in the interstices of the tissue or in 

 the blood-passages is more difficult to decide without injections. 

 Fortunately the numerous blood-corpuscles intermixed with 

 them help us into the right road ; we have to do only with 

 blood-sinuses, as, moreover, the form and distribution of the 

 spaces filled with the green cells would almost alone render 

 certain. The injection effected by them is frequently so 

 perfect as to give us a distinct picture of the lacunar system in 

 the mantle; and of the subepithelial layer of the mantle- 

 tissue we sometimes obtain representations which to some 

 extent resemble those recently given by P. Schiemenz *. In 

 this way we are taught that the flask-shaped organs must be 

 surrounded by large blood-sinuses, as an enormous accumula- 

 tion of green cells regularly occurs around them. On the 

 other hand, in the larger vessels with distinct walls which 

 are distributed in the mantle I have never met with green 

 cells. 



The only observation of the occurrence of pseudochloro- 

 phyll-corpuscles in Mollusca that literature has to show is 

 due to K. Brandt and relates to Elysia viridis f. In this 

 species they lie in the " system of contractile tubes in the 

 mantle; '^ what Brandt means by this is somewhat obscure, 

 but we may not be much mistaken in assuming that the vas- 

 cular system is referred to. This would agree with Tridacna ; 

 but in other respects there is considerable difference in the 

 green cells of ELysm according to Brandt's description and 

 figures [loc. cit. figs. 90-93). They are much smaller and of 

 much more irregular form than those of Tridacna, and the 

 emerald-green colouring-matter is not localized in separate 

 granules, but uniformly permeates the protoplasm. 



As is well known Schmitz J has recently adduced evidence 



* Paulus Scliiemenz, " Ueber die Wasseraufnalime bei Lamellibranch- 

 iaten und Gastropoden," II., Mitth. Zool. Stat. Neapel, Ed. vii. Heft 3, 

 Taf. xvi. figs. 8, 9. 



t K. Brandt, " Ueber die morpbologische und physiologische Bedeu- 

 tung des Chloropliylls bei Thieren," iu Mitth. Zool. Stat. Neapel, Bd. iv. 

 p. 243. 



X F, Sclimitz, " Die Chromatophoren der Algen," in Verb, naturb. 

 Ver. preuss. Rheiul. und West!'., Jahrg. si (1883) p. 1. 



