NoTT. — On N.Z. Composite Ascidians. 307 



microtome, but time did not permit the completion of my in- 

 tention. This is all the more to be regretted in this case as 

 the accounts of the genus available are very meagre, and the 

 complete examination I was able to make of the test proves in 

 our New Zealand forms a remarkable amount of speciality, 

 which might possibly be reproduced in the internal structure. 



Canada balsam and glycerine were used as mounting 

 media — chiefly the former, though in many particulars glycerine 

 excels, as in the case of Cystodytes. Wherever any special 

 mode of treatment gave desirable results the fact will be speci- 

 fied in the second part of my paper, so that any lengthened 

 mention here is out of place. 



For microscopical examination, a Crouch's stu.dent's micro- 

 scope, with eyepiece 3 and Zeiss's a'-'' objective, was used for 

 low powers, being useful chiefly in the case of Cystodytes. In 

 all other cases a Zeiss instrmnent with oc. 2 and objectives 

 A, C, E, and P was employed, every part of each section being 

 carefully examined with obj. A, and details referred to the 

 higher powers when necessary. As some hundreds of sections 

 contaiuing thousands of zooids were thus passed under review, 

 the work was naturally tedious, but none the less interesting, 

 and, I hope, profitable. 



Drawings were made of all the species, the accompanying 

 plates being so designed as to show all points of interest as ftir 

 as possible. I believe that these plates, with their accom- 

 panying explanatory notes, will speak for themselves as to 

 their mode of production : here, however, I may briefly state 

 that drawings of the colony in complete section were, unless 

 otherwise specified, inade from the sections directly, using 

 obj. A. The thickness of the colony at the point of section 

 "was carefully determined by a millimetre scale, and the draw- 

 ing afterv^ards copied, using the scale to determine the amount 

 of enlargement. Thus, Cystodytes aucklandicus measures 

 exactly 5mm. in section naturally : the fig. (1 in PL XXX.) 

 is enlarged 7 diameters. In some few instances the drawings 

 have been made without much attention to scale, but generally 

 an attempt has been made to so use the camera that a fair 

 comparative test of the corresponding parts in different species 

 may be arrived at. To this end a drawing-table was placed 

 by the side of the microscope, and thus the distance traversed 

 by rays of light was in all cases the same, the height of the 

 table being constant, and such as to reduce the outlines to a 

 suitable size. Each figure has an explanatory note giving the 

 objective used, and stating whether the camera was employed 

 or otherwise. A Zeiss's " Abbe " camera was the instrument 

 thus us3d. 



It only remains for me to notice the works of reference 

 available. These are not numerous, nor can I suppose that 



