Befroductive Condition of Orbitolites, &c. By H. B. Brady. 697 



correspond to Form A, but that after a process of resorption of the 

 large central chamber, the animal constructs a series of new chambers 

 corresponding to Form B." * The authors further state, as an 

 objection to the alternative theory of the distinct origin of the two 

 forms, that they " have not been able to discover amongst the numerous 

 species they have studied any very young individuals of Form B." 

 The case before us, in which the young individuals taken from the 

 parent shell exhibit the large initial chambers, whilst in the parent 

 itself the centre is occupied by numerous chambers of relatively minute 

 size, gives great weight to the former explanation. 



The question naturally arises, whether the embryonic forms which 

 have been described are the result of sexual intercourse of any kind, 

 or simply of a process of gemmation. With reference to the " di- 

 morphism " of the Foraminif'era, Mr. Geddes has suggested that " the 

 better grown and less modified " shell " with fewer partitions and a 

 ' grand loge central ' seems distinctly the anabolic or female, the other, 

 since smaller and more modified, the male ; " j but as yet this view is 

 founded on analogy rather than direct observation. The probabilities 

 in the present case are in favour of simple gemmation, and, if this be 

 correct, the mere fact of the presence of very young shells in the 

 manner described has no bearing either way on the question of sex. 

 On the other hand, it must be admitted that the change of the 

 individual from one form to the other, if clearly established, would 

 render the sexual theory superfluous. 



It is possible that the same explanation may serve both for the 

 plicate margin of the discs and the production of large broods of 

 young individuals, and that both may be due to redundant growth 

 consequent upon exceptionally favourable external conditions and a 

 plentiful supply of food. 



It is to be regretted that none of the specimens were preserved in 

 alcohol. Verworn has recently shown that the presence of a nucleus 

 is essential to even simple, scarcely more than vegetative, processes 

 amongst the Foraminifera,t and it would have been interesting to 

 trace the relation, which may be assumed to exist, between the 

 numerous minute nuclei, found by Biitschli in the plasma of the 

 peripheral chambers of the Orbitolite § and the young individuals 

 which make their appearance in such abundance in the same portion 

 of the test. 



* Comptes Kendus, xcvi. (1883) p. 1601. 



t Proc. Eoy. Soo. Edinb., xiii. (1886) p. 931. The idea originated with de la 

 Harpe, but does not appear to have been seriously entertained by him. 

 X Zeitschr. fur Wiss. ZooL, xlvi, (1888) pp. 455-470, pi. sxxii. 

 § Morph. Jahrb., xi. (1885) p. 80, &c., pi. vii. figs. 1, 4. 



