14 Transactions of the Society, 



the number of small individuals in a dredging would very largely 

 exceed that of the adult individuals. Such, however, is not the 

 case. Adult, or semi-adult tests are always present in a Saccam- 

 mina dredging in greater numbers than the smaller specimens. 



As regards the second theory, which appears to have been 

 accepted by Dr. Ehumbler with great reluctance, there is, in our 

 opinion, no reason to doubt that Saccammina, like most other 

 organisms, possesses absorptive as well as secretional powers. 

 We believe that the process of secretion is, in the Arenacea, as in 

 the more easily studied perforate group, carried out with great 

 rapidity when in actual operation. The animal having outgrown 

 the accommodation afforded by its rigid house, probably gathers 

 together a fresh supply of building material in its extruded proto- 

 plasm. The old house is rapidly dissolved, under the action of 

 some solvent secreted by the protoplasm. The new and the old 

 material are then, as it were, cast into the melting-pot together, 

 and reformed into a new test on the surface of the protoplasmic 

 or sarcode-body, now retracted into a mere globule of protoplasm. 

 This process would be assisted by the well-known action of surface- 

 tension. As evidence of this we may point out that, in dredgings 

 where the form occurs in any abundance, specimens are occasion- 

 ally to be found which have been caught and brought up by the 

 dredge just at a moment in their life-history when the process of 

 shell-construction, or rather of cement-secretion, was in a relatively 

 unfinished state. The shape of the test is complete, but the 

 cementing together of the sand-grains is incomplete, and conse- 

 quently such tests are extremely friable, and are liable to collapse 

 at a touch. (Plate II, fig. 2.) 



For the reasons given above we are unable to follow or agree 

 with the niasterly and laborious researches of Dr. Ehumbler, and 

 the ingenious deductions that he has made from them. 



To turn to the results of our own collections and examinations, 

 the whole balance of evidence appears to us to contradict the de- 

 ductions of Dr. Ehumbler. Leaving the question of the Primativ- 

 gehduse on one side, the whole of his theory must stand or fall by 

 the distribution of the two types. If Saccammina sphaerica. is the 

 parent of Psammosiphxra fusca, the two forms should occur to- 

 gether. Such, however, is not the case in the North Sea. 



A brief analysis of the results, which we have tabulated at full 

 length and with some detail, will show at a glance the respective 

 distribution of Saccammina and Psammosphmra, whether isolated or 

 accompanying one another, and whether under these circumstances 

 they are numerous or rare. 



From our figures we have no hesitation whatever in confirming 

 the separate identity of the two genera, and we may now proceed 

 to analyse and to amplify the details concerning the respective 

 species, from an observation of the specimens which we have col- 

 lected and recorded. 



