8 Transactions of the Society. 



Before proceeding to the analysis of our own data, it may be 

 as well to discuss some of the evidence tendered by Dr. Ehumbler, 

 and to consider to what extent it has value in the consideration 

 of the postulated, and by us disputed, identity ( Vereinigung) of the 

 two forms. 



It will be useful in this place to reproduce Dr. Ehumbler' s 

 short summary of his theory of the processional development of 

 his completed Saccanimina (6, p. 455). 



" Following upon the above statements, one can discriminate 

 the following seven stages in the Test-development of Saccammina. 



(1) For the most part kidney-shaped primordial tests, with a 

 primitive surface-cover consisting of several layers of very small 

 stones. 



(2) The primitive-cover has become thicker and larger ; 

 numerous sponge-spicules are embedded in it. 



(3) In place of the sponge-spicules, larger stones are taken 

 into the primitive-cover. With the increase in the number of 

 these stones, the number of the sponge-spicules decreases, and is 

 finally reduced to zero. 



(4) The larger stones displace the primitive-cover more and 

 more. Some sparse and fortuitous relics of it may remain behind 

 as mortar-mass. The larger stones are, as it would appear, cemented 

 together quite irregularly. 



(5) The stones are arranged into the flat surface of the shell- 

 wall with their flat sides outward. The outer aspect of the tests 

 is thereby rendered much smoother. The commencement of the 

 aperture-crater (Pylomrohre) is indicated (angelegt). 



(6) The chinks and fissures which cause the edges of the 

 stones to gape apart on the outer side of the tests are filled up 

 with mortar-mass. The aperture-crater rises up over the sur- 

 rounding stones. 



EXPLANATION OF PLATE IL 



Fig. 1. — Saccammina siihierica M. Sars. Sessile specimen attached to Molluscan 

 shell. 



,, 2. Ditto. Loosely agglutinated specimen, in which the process of forma- 

 tion of a new test is incomplete. 



,, 3-5. — Psamm,osphsera fusca Schulze. Free normal type. 



,, 6. Ditto. Faroe Channel type, employing sponge spicules in construc- 

 tion of test. 



,, 7. — P. fusca Schulze vav.parva Flint. 



,, 8. Ditto. Spicule-selecting form. 



,, 9. — P. fusca var. testacea Flint. Test constructed of Uvigerina pygmsea 

 d'Orbigny. 



,, 10-16. — P. fusca Schulze. A series of sessile specimens illustrating the 

 gradual passage from the normal type built up of sand-grains to 

 a type constructed entirely of cement. 



All figures magnified 35 diam. 



