244 i?. J. L. Giqypy — Foraminifera of Trinidad. 



The term Sagrina is superfluous, as pointed out by Brady (Chall. 

 Eep., p. 580). The name Uvigerina sufficiently covers the forms so 

 named. Uvigerina as well as Spiroplecta shows a cristellarian 

 commencement. Uvigerina is the form connecting Fohjmorphina 

 through Cristellaria with Nodosaria, while Spiroplecta is the 

 analogous arenaceous form. The biserial and triserial forms of the 

 arenaceous Foraminifera passing into uniserial forms are due to their 

 descent from Polymorphina. Very minute Textularians as well as 

 Bolivina often show a similar kind of commencement. 



Goes ("Arctic and Scandinavian Rhizopoda," p. 6) gives figures 

 of three forms of Frondicularia, two of which closely resemble those 

 I have given in P.Z.S., 1894, pi. xli, figs. 3, 4. His observations are 

 entirely in accordance with mine. He says : " Thus in this instance 

 we have before us the plainest proceeding of evolution from one 

 type to another, in which an earlier type becomes larva for another 

 type. At last the larval condition is reduced to a single segment, 

 and a new form has originated seemingly standing without much 

 morphological connection with its origin." He further remarks that 

 the smallest embryo segments do not always give rise to a dimorphous 

 form, but at once assume the mature arrangement of the segments. 

 This is exactly what I pointed out in my paper above referred to. 

 Thus Flahellina is not a genus, but merely represents those 

 Frondicularias that retain an embryonic cristellarian commencement. 

 That these were more abundant in the past than they are at present 

 is natural, for the tendency would ever be for the embryonic form to 

 pass at once to the mature form. And this condition is not confined 

 to Foraminifera, but is exhibited in species belonging to Crustacea, 

 Insecta, and Mollusca. These, as they increase by interstitial and 

 not by incremental growth, do not permanently show the embryonic 

 form, though Mollusca do so to some extent. They pass through 

 the embryonic stages, and the embryonic condition can only be 

 observed while they are passing through it. But Foraminifera, 

 growing by stages and each stage being retained as part of the 

 mature organism, show more or less all the stages they have passed 

 through from the first segment. 



We have not yet arrived at a true appreciation of the full 

 significance of the various characters of Foraminifera. Doubtless 

 we shall do so after careful study and comparison. Without being 

 able myself to point out all the significance of the facts, I may still 

 advert to some of them. 



The close affinity between Nodosaria, Uvigerina, and Pohjmorphina 

 has long been acknowledged by rhizopodists. It is stated by 

 Carpenter (Introd., p. 168). It is only the order of their development 

 and affinity that has been matter of doubt. The aperture of 

 Nodosaria is normally circular with radiating fissures or grooves. 

 This aperture is characteristic of Polymorphina, Cristellaria, and 

 Frondicularia. In some Nodosarians the radiating fissures are 

 obsolete or disappear, and the aperture becomes simply circular, 

 often at the end of a neck which is usually everted and encircled by 

 ridges spiral or circular. In other forms, the test being oval in 



