5)71 SUMMARY OF CDIIUENT RESEARCHES RELATING TO 



ftutcrior end. This canal is so fine as to be often invisible in the living 

 animal, but it can be demonstrated with certainty by the aid of osmic 

 acid. Unlike the sucking tubes of most Acinetro, this canal is not 

 continued into the interior of the cell. If one of the tubes of a lively 

 specimen is fixed for a few minutes, the extreme tip raises itself from 

 the tentacle as a distinct tentaculet, which is pushed out and retracted 

 several times a minute. The object of this movement is not clear. The 

 tentaculets very probably secrete a viscid substance, for very small 

 flagellates were often observed adherent to them ; in the case of 

 such small organisms the nutriment is simply pumped into the tentacular 

 canal by means of the tentaculet. 



The reproduction of Asellicola is exactly similar to that of Dendro- 

 comctes paradoxus, but the process of conjugation exhibits an essential 

 difference. As the Asellicolse do not, as a rule, stand so close as to 

 touch each other, those individuals which are about to conjugate are 

 almost always compelled to unite themselves by a process of the body. 

 For this purpose a tentacle at one end of the body grows enormously 

 beyond its ordinary size ; sometimes one only, sometimes both devclopo 

 a conjugation-tentacle. This tentacle is slowly moved to and fro until 

 the object is attained. When the two animals are united the conjugation 

 canal becomes thicker and thicker, as more of the body-substance from 

 both sides passes into it. Although the cytoplasm of the two animals is 

 very intimately mixed in the canal, the distinctness of the two individuals 

 is not effaced, for, on the least disturbance, the cell-bodies separate from 

 each other in the middle of the canal and lie near each other, covered by 

 a thin membrane. When the canal is completed it swells up, and the 

 nuclei of both individuals migrate into the canal of union and towards 

 one another. They do not, however, seem to come into contact, and 

 they at this time undergo no change of structure, but the author believes 

 that they reciprocally influence one another. After this is effected, the 

 nuclei return to their original position ; the plasma returns from the 

 canal of union into the cell-body, and rupture is effected. The nuclei 

 then begin to divide, and finally break up into a number of larger and 

 smaller pieces, which are scattered through the whole of the cell-body. 

 In general it is medium-sized individuals that conjugate, while those 

 that arc full-grown form buds. 



Acinetoides.* — Dr. L. Plate gives an account of a new genus — which 

 he calls Acinetoides — intermediate between the ciliated Infusoria and the 

 Acinetae. His examples were found on colonies of Zoothamnium from 

 the Bay of Naples. The larger species is called A. Graffi, and the 

 smaller A. zoothamnii. The anterior end projects beyond the ventral 

 margin of the body in the form of a low cone, bearing in its middle the 

 organ for the inception of nourishment, a sucking thread clubbed at its 

 extremity ; this may be traced far into the interior of the cell-body, and 

 is distinguished only by its remarkable shortness and rigidity from the 

 similar organs of most other Acinetse. The ventral surface has an 

 elliptical inner area ciliated ; the cilia are arranged in longitudinal rows, 

 and appear to be placed in special grooves. The ventral surface is 

 highly contractile. A. zoothamnii was observed to undergo transverse 



* Ann. and Mag. Nat. Hist., ii. (1888) pp. 201-S. Translated from Zool. 

 Jahrb., iii. (1888) pp. 1^5-43 (3 figs.). 



