472 A " Colonial" Herbarium Specimen. [Sess. 



flinty skeleton of the diatom — the frustule — reminds one of 

 the condition of two joints of a closed telescope, the margins 

 or lateral walls of one half completely overlapping those of 

 the other. Under the vital action of the protoplasm the inner 

 half slips out of the embrace of the outer, and both acquire a 

 new wall at their unprotected face. The inflected edge of the 

 new walls are embraced by and telescope with the existing 

 margins of the respective halves. It thus follows that the 

 individuals of succeeding generations derived from the series of 

 inner halves become smaller and smaller. A stage is reached, 

 however, when the fate of being lost in infinity of subdivision 

 is averted. The contents of valves at their minimum emerge, 

 and either themselves grow into larger proportions, or enter 

 into conjugal fellowship with others of a like nature to form 

 large cells known as auxospores. These secrete a silicious 

 framework of the maximum size, and inaugurate a new cycle. 

 Diatoms are mostly buff-coloured, by reason of the presence 

 of a substance termed diatomine, which hides the chlorophyll. 

 They are generally endowed with somewhat limited loco- 

 motion, which is understood to be effected by the protrusion 

 of protoplasmic processes, recalling pseudopodia, along certain 

 definite lines. Besides the comparatively large diatom Isth- 

 mia, there are at least four others in company with it. 

 A minute elliptical species in great numbers, lying like scales 

 on many parts of the specimen, is Cocconeis. The others, 

 including Grammatophora, are in closely jointed or loosely 

 linked chains or rows. 



So much for the flora of our colony : let us look now at its 

 fauna, taking the lowest forms first. At many points there 

 will be found microscopic spiral white shells, simulating those 

 of shell-fish. They belong to foraminifera — organisms in- 

 ternally little better to all appearance than specks of jelly. 

 From the mouth of the calcareous shell there protruded, when 

 the inmate was in life, long, delicate, occasionally anastomos- 

 ing strands of protoplasm (sarcode) covering the shell, and 

 feeling about, amceba-like, in quest of food. They also acted 

 as feet, enabling the shell-bearer to move about. The mode 

 of reproduction is not well understood. Foraminifera, small 

 as they are, have played an extremely important part in the 

 upbuilding of the earth's crust. They form large masses of 



