231 [Clark. 



Members: — W. M. Ogden, Dr. J. F. Frisbie; Messrs. E 

 Bicknell, W. S. Whitwell, W. S. Chase, Alanson Tucker of 

 Boston, and Mr. B. P. Mann of Concord, Mass. 



November 15, 1865. 

 The President in the chair. 



Forty-three members present. 



Prof H. James Chirk made a communication on the ves- 

 tibular bristle of Vorticellidie. 



The so-called " bristle of Lachman" is an optical illusion. 

 Two rows of vibrating cilia may be traced fi*om the stem of the 

 vibrating organ of Epistylis {JE. galea Ehr ? and JE. grandis 

 Ehr ?) into the aperture of, and to the very bottom of the 

 vestibule. One of these rows of cilia lies on the right side 

 and the other on the left side of the mesial line of the vestibule. 

 The one on the left, in particular, has a very strong resem- 

 blance to a single lash or bristle. This arises from the peculiar 

 mode of arrangement of the cilia. Outside of the vestibule 

 they are extended in comparatively straight, parallel Unes, 

 but when they enter the body they curve upon themselves 

 in such a way as to form collectively a sort of cylinder; so 

 that the vestibule appears to be lined with a series of closely 

 approximated rings or hoops. From whatever point of view, 

 therefore — excej^ting when looking directly into its mouth — 

 the vestibule is seen, the outline of its cyhnder of cilia ap- 

 pears as a single line^ vibrating more or less, according to the 

 activity of the component elements. Inasmuch as these two 

 rows of cilia are quite wide apart in Epistylis, there always 

 ajDj^ear to be two false bristles within the vestibule ; but as a 

 general thing the one on the right is very fiint. In Carche- 

 sium ( C polypinmn Ehr.) and V^orticella ( V. nebulifera 

 Ehr.) the two rows are so close together that very rarely 

 more than one filse bristle can be seen. In Trichodina (^T. 

 pedieulus Ehr.), the vestibular ciha forms but one single 

 continuous Hne, and in consequence of this there seems to 

 be but one false bristle. In perfectly fresh specimens of 

 all the above mentioned Vorticellidans the illusion is most 



