100 SUMMARY OF CURRENT RESEARCHES RELATING TO 



ciliated combs or pectiuellae, which are composed of numerous fine cilia, 

 whose connected basal portions form the transverse ridges of the ciliated 

 organ. Prof. Mobius also describes the multiplication of Freia amjmlla 

 Miill. by unequal longitudinal division. 



Contractile Vacuoles of Infusoria.* — Herr S. Fischer has investigated 

 the contractile vacuoles of AspkUsca lynceus and Paramsecium aurelia. The 

 former infusoriau had three pulsating vacuoles ; the largest to the right 

 of the mouth with regular pulsations ; the second of smaller size and 

 posterior position, with pulsations alternating with those of the former ; 

 while the third and smallest exhibited irregular and less frequent pulsations. 

 At the maximum diastole of the largest a thin drop appears close beside it, 

 which increases gradually during the systole, and becomes the new vacuole. 

 In Paramsecium the vacuole at its maximum extension is surrounded by a 

 system of delicate canals, slightly swollen at a certain distance from the 

 vacuole. During the systole the swollen extremities gradually come into 

 contact to form a new vacuole. There is thus no definite membrane round 

 the vacuoles. The contents were seen in Asjndisca to be expelled to the 

 exterior. The pulsations are accelerated in deficient aeration of the water. 



Bursaria truncatella.j — Herr A. Schuberg has studied Bursaria trunca- 

 tella W'ith special reference to protoplasmic structures. For the purposes 

 of fixation he made use of the vapour of osmic acid, or, in preference, of 

 Flemming's mixture of chromic, osmic, and acetic acid, especially as 

 modified by Fol. After washing in water, and being placed in 1 per cent, 

 osmic acid till they were slightly brow^ned, the infusorians were ready for 

 clearing up and preservation in Canada balsam. Sections were made after 

 the object had been completely blackened by osmic acid, and further 

 stained by strong Bohmer's haematoxylin. 



The author commences by pointing out differences from the usually 

 received accounts ; he was not able to detect a complete symmetry, the 

 greatest thickness of the hinder end of the body being somewhat towards 

 the left side ; the anterior end is always oblique. There appears to be 

 some variability in the peristome; this portion arises from a straight 

 peristome which lies quite free on the surface, undergoes a gradual in- 

 sinking and a correlated spiral inrolling of the adoral zone ; with this 

 there may be connected that development of a septum which is due to the 

 greater growth of some parts. Directly connected with the peristomial 

 cavity is a space, the true relations of which seem to have escaped all 

 previous observers. Though the form of the peristome varies considerably, 

 it is always deepest on the right side of the animal, and its dorsal wall is 

 hollowed out on the ventral aspect ; towards the base of this cavity a 

 septum becomes developed, and separates off a septal space ; this septum is 

 the only part of the peristome that carries cilia. 



The origin of this arrangement is explained thus : As, cotempo- 

 rancously with the peristomial cavity, the hinder edge of the peristome 

 grows forward in such a way that a flattened bridge extends from the left 

 peristomial margin over the right margin, a cavity must be formed which is 

 connected with the peristomial cavity at its hinder end, as well as along 

 its left side. The boundary of this septal space on the side of the 

 peristomial cavity, which are now only connected by a relative narrow cleft, 

 is naturally formed by the primitively right peristomial margin, beset with 

 cilia. Since the growth of the hinder peristomial margin did not take 

 place along the right margin, but in a line somewhat more to the right, the 



* Arcb. Slav, de Biol., ii. (188G) pp. 288-9, from Wszechswiat, 1885. 

 t Morphol. Jahrb., xii. (188G) pp. 307-65 (2 pis.). 



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