758 SUMUARY OF CURRENT RESEARCHES RELATING TO 



these cilia and those just described. All the rest of the surface of 

 the body of the species observed was smooth. 



After briefly criticizing Claparede and Lachmann, and Stein's 

 descriptions of the ciliation of the Tintiunodea, Professor Fol states, 

 that on the surface of the disk, in the neighboui-hood of the mouth, 

 there is a slight crescentiform projection, which rises above the side 

 on which the margin of the orifice forms an acute angle (see Fig. 8). 

 "Whether this projection is comparable to the part that Stein describes 

 nnder the name of '• forehead " is uncertain ; but it has no relation, 

 near or distant, with the disk of Yorticellina. 



The nucleus is very difficult to see. It can hardly be discerned 

 except in starved individuals. "Whenever believed to be observed it 

 appeared to be situated in the upper part of the body, and to present 

 an oval form (Fig. 9). Sometimes Professor Fol believed he could 

 distinguish a contractile vacuole in the inferior region of the body 

 (Fig. 9). 



The test is composed of a hard, slightly elastic material, which, 

 however, breaks when the pressure is slightly increased. It resists 

 acids even where tolerably concentrated, and presents no evolution 

 of gas ; therefore it is not an earthy carbonate. It burns away 

 entirely at a dull red heat ; hence it is not silica. It resists for a 

 long time the action even of tolerably concentrated alkalies ; con- 

 sequently it is not a horny substance. There remains only chitine. 

 The test generally presents two distinct layers, which, however, 

 to all appeai-ance, are of the same chemical composition. All the 

 tests hitherto observed may be referred to three types, which seem at 

 the first glance very distinctly marked — namely, smooth tests, tests 

 garnished with adherent foreign particles, and latticed tests. How- 

 ever there are species which establish the transition between the 

 smooth tests and the tests with adherent particles ; and on the other 

 hand, among the latticed tests, that which the author observed was 

 continuous and only hollowed out by a number of small cavities on 

 its outer surface. It was not jierforated, which approximates it to 

 certain smooth tests presenting patterns on their outer stu'face. 



Professor Fol has not succeeded in observing the reproduction of 

 these animals, though he frequently witnessed their conjugation. 

 The presence of the test is not an obstacle to conjugation. The 

 individuals do not quit their tests in order to unite ; they amalgamate 

 by the margin of the peristome. The point of union is absolutely 

 constant ; it is situated in the vicinity of the mouth, but a little to 

 the left of the latter in such a way that two individuals in conjugation 

 always form a perfectly symmetrical figure (Fig. 8). The union 

 is tolerably extensive and very intimate, and lasts for several hours. 

 During this time the copulated individuals cannot withdraw into 

 their tests ; their natation is however almost as rapid as that of the 

 isolated individuals. 



Turning next to the question of classification, Professor Fol 

 traces the history of the group. 



The genus Tintinnus was established by Otto F. Miiller in 1776, 

 and made to include a whole miscellaneous group of diverse forms. 



