FseudochlorophijU-corpuscles in Tridacna. 445 



which show in their structure a decided resemblance to the 

 flask-shaped organs, the so-called " eyes " on the tentacles of 

 Cardium (see Patten's figure, /. c. Taf. xxxi. fig. 112), are 

 unfortunately very doubtful as regards their function, 

 although the opinion that they are luminous organs is by no 

 means to be regarded as disproved *. 



It is well known that the symbiosis of unicellular Algse 

 with Evertebrata of the most different classes discovered by 

 Geza Entz and K. Brandt has never ceased to be a matter 

 of the most lively interest. 1 believe, therefore, that I shall 

 earn the thanks of many by adding to the known cases of this 

 symbiosis a new one which may claim the greater interest as 

 only one instance of the kind among the Mollusca is to be 

 found in literature. The very first incision which I made 

 through the mantle-margin of a Tridacna showed me, to my 

 astonishment, all the available interstices of the tissue densely 

 packed with "green cells" (pseudochlorophyll-corpuscles), 

 and, as I found in the course of my investigation, this con- 

 dition prevailed in all my specimens and in all parts of the 

 mantle. It is true that the interest which would otherwise 

 attach to this discovery was considerably weakened by the 

 circumstance that it was made only on preserved animals. 

 As the strict scientific proof that the colouring-matter of these 

 green cells is chlorophyll can no longer be produced, readers 

 of too critical a disposition may be inclined in regard to the new 

 discovery to pass to the order of the day. In opposition to 

 this I would point out that my only purpose here is to com- 

 municate briefly the observations made, which I am justified 

 in doing, and, to a certain extent, obliged to do. When once 

 attention is directed to these things the investigation of the 

 questionable chlorophyll in fresh material will probably not 

 have to be very long waited for. 



Tlie " chlorophyll-corpuscles " in question are certainly 

 true cells, as, without exception, they possess an approxi- 

 mately central small nucleus with a distinct nuclear frame- 

 work, which becomes very deeply coloured in the staining 

 reagents employed (Grenacher's alum-carmine). In general 

 the nucleus is spherical, but sometimes obloug or reniform, 



* Carriere (' Die Sehorgane cler Thiere/ Mimich, 1S35, p. 97) certainly 

 ob>served no spontaneous liuninosity when the outer light was excluded ; 

 but a function dependent upon nerve-iuiiueuce, such as luminosity cer- 

 tainly is, need not occur at all times. 



