356 SUMMARY OP CURRENT RESEARCHES RELATING TO 



becomes more and more distended, so as to include as much as tliree- 

 fourtlis of the breadth of the body. It is scarcely probable that an 

 unusually thin membrane in connection with the vacuole, if present, 

 should be able to stretch to such an extent, without bursting, a con- 

 sideration which appears to furnish additional evidence in favour of 

 the absence of a membranous wall in the vacuole. Limbach, by 

 observation of Vorticella cyathina during fission, has been able to 

 determine the opening of the vacuole into the vestibule, and the 

 expulsion of its liquid through the opening of the latter. The same 

 results were obtained from the abnormal Vorticelice above mentioned. 

 Thus the contractile vacuole constitutes an excretory organ, although 

 it may at the same time assist in the function of respiration. 



Geographical Distribution of Rhizopoda.*^ — C Parona gives a 

 review of the lihizopoda found by Leidy in North America, of those 

 met with at the same time in Europe, and finally of those found since 

 then in Italy. The astonishing agreement in the Protozoan faunas 

 of districts so widely separated prompts him to raise the question 

 whether the laws of phylogenetic development are hereby modified, a 

 question which he answers negatively. This agreement is explained, 

 according to his view, by the original derivation of the Protozoan 

 faunas of both regions from a common source, and this must un- 

 doubtedly have been a marine source.| The closely similar alter- 

 ations which have taken place in the circumstances and manner of 

 life which the primitive Protista-faunas of the two continents have 

 undergone in the course of ages, are considered by the author to have 

 gone so far as to caitse even the development of closely similar furms. 

 He is therefore inclined, at any rate in this case, to admit a poly- 

 phyletic origin of species. 



Classification of the Gregarinida.| — B. Gabriel puts forward in 

 two places a new classification of this group, based on his investiga- 

 tions into the process of reproduction in the Gregarines. He has 

 been led to take this course by finding the principles advanced up 

 to the present time by Stein and Schneider, and depending essentially 

 upon the morphological peculiarities of the mature forms, to be in- 

 sufficient ; he therefore believes that a classification can only be based 

 on the reproductive relations of these organisms. The presence or 

 absence of a septum (the point of distinction between Mono- and 

 Polycystidfe of Stein and Schneider) has in his eyes no deep im- 

 portance, inasmuch as he has found at Naples, in Typton spongicola, 

 a Gregarine, which in its early life is a septum-less Monocystidean, 

 but acquires later not only one, but numerous transverse septa, and 

 thus presents a colonial or strobila-form which arises by terminal 

 budding, and whose segments are individually capable of in- 

 dependent reproduction. Gabriel finds the attaching apparatus of 



* Bollet. Scientif., ii. (1880) pp. 43-50. Cf. Zool. Jahresber. Neapel for 

 1880, i. p. 127. 



t Prof. 0. Butschli (loc. cit.) remarks on this that this opinion might be ex- 

 tended with probable accuracy to all fresh-water faunas. 



X Ber. Versamml. deutsch. Naturforscher u. Aerzte, 1880, pp. 82-3. Cf. Zool. 

 Jahresber. Neapel for 1880, i. pp. 160-1. 



