222 W. H. GILBURT ON THE RELATION OF SPH^ROSIRA VOLVOX, &C. 



became more marked, and under a power of 350 diameters those 

 which departed from the supposed normal character appeared as in 

 Fig. 2, viz., a sphere as an ordinary Vol vox, but that some of the 

 gonidia were missing, and their places occupied by compound bodies, 

 as at Fig. 2b — in this and every other respect agreeing with the 

 figures of Sphcerosira as given both by Ehrenberg and Busk. 



Submitting them to pressure so as to rupture the cell wall, I 

 found that the compound bodies referred to escaped; and then 

 appeared as at Figs. 3 and 4— Fig. 3 being a front view and 4 one 

 in profile, as seen under a power of 600 diameters. They are 

 discoid in form, and composed of about thirty cells, flask-shaped — 

 as Fig. 5 — having a nucleus, being attached to each other by the 

 smaller end, and furnished with abundant vibratile cilia, which can 

 be seen in both aspects as figured. The action of the cilia imparts 

 a slow, revolving, wheel-like motion to the group, but with very little 

 progression. This motion can sometimes be seen while they are still 

 within the containing sphere. In a single Sphcerosira as many as 

 55 of these compound bodies have been found. 



One most remarkable feature is, that while the Volvox globator 

 may contain from two to seven macro-gonidia, yet in only two 

 instances have I found more than one Sphcerosira among them ; 

 though a very large number have been examined for this special 

 purpose. 



Another circumstance to be taken notice of is, that where a 

 Sphasrosira is found, although the appearance of the other macro- 

 gonida is of the normal character outwardly, yet still a difference 

 exists; for attached to the interior of the cell-wall are certain bodies, 

 represented in Figs. 6 and 7 — Fig. 6 showing one in situ, and Fig. 

 7 one under pressure, and magnified 600 diameters. They appear 

 to consist of a roughly spherical mass of protoplasm, pale-green in 

 colour, but unevenly tinted, with darker spots, having well-marked 

 nuclei or vacuoles. These seem to me to be very unusual in 

 character, and, taken with the Spha'rosira which we have found 

 occupying the same mother-cell, appear to suggest a relationship 

 between them — possibly sexual. 



Note. — Since reading the foregoing paper at the October meeting 

 I have found the compound bodies free in the water. They have 

 then a vigorous oscillating motion, turning so as to show in profile 

 at each limit of its swing. 



