354 Dr. E. von Daday on a 



follows the results of my observations. The outline of tiie 

 primordial chamber is always circular; this chamber appears 

 to be perfectly round, at least its outer free surface decidedly 

 represents a segment of a sphere. The second chamber is 

 somewhat elongated ; its anterior extremity {i. e. the one 

 which is in contact with the primordial chamber) is conically 

 pointed, while the posterior end is enlarged. All the following 

 chambers form truncated triangles, of which the base is con- 

 vex, while of the sides the one is curved inwards, the other 

 outwards. Variations of form are frequent but insignificant. 

 On the whole it may be said of the form of the chambers that 

 it remarkably agrees with that of the chambers of Rotalia 

 venetttj M. Sch., Rotalia Frei/eri, M. Sch., and Rosalina 

 ornata, d'Orb. (see Max Schultze, ' Ueber den Organismus 

 der Polythalamien,' Taf. iii. figs. 1, 2, 4, 6, and 8). 



The septa of the individual chambers are very cliaracteristic 

 of the genus, and agree in structure in all the chambers except 

 the primordial one. The septum of the primordial chamber 

 is not particularly developed, and only forms the correspond- 

 ing completion of the rest of the wall of this chamber. The 

 structure of the septum of all the other chambers is shown 

 most distinctly by the anterior wall, that is to say, the oper- 

 culum of the last chamber, when the shell standing on its 

 edge is looked at from in front. We then see that the septum 

 consists of two symmetrical halves, which meet together in 

 the middle line like a roof, and to a certain extent seem 

 to be independent portions of the shell. The whole septum 

 is more or less convex — a condition which appears most 

 distinctly in transverse sections. 



My investigations led me to the conviction that the septa 

 of the chambers, as in the Ilotalina3, are formed by two 

 lanicllas, one belonf^^ing to the anterior, the other to the pos- 

 terior chamber ; but that in one species these lamellae enclose 

 no interseptal space, the boundary between the two lamellje 

 being indicated only by a sharp line. The rather thick septa 

 thus formed are not perforated with fine pores any more than 

 the other parts of the shell ; but instead of these, two small 

 round apertures and two larger oval ones are present, and 

 these both morphologically and physiologically represent 

 the fine orifices of the Rotalina^ and the otiier Polytlialamia 

 in general. By these four apertures the chambers are placed 

 in communication with each other and the last chamber with 

 the outer world. 



The two smaller round apertures and two larger oval ones 

 in the septa are extremely characteristic of our P(jlythalamian. 

 Their position can be most certainly ascertained when the 



