196 Prof. H. James-Clark on the Spongige ciliatje 



24, 24^), and frequently much longer; but In the latter case it 

 was sometimes observed to arise from the falling away of one 

 of the resultants immediately after self-division occurred. It 

 has a uniform thickness, or occasionally the slightest possible 

 taper, from base to apex, and appears to be solid and homo- 

 geneous in texture. It is apparently inflexible, and, even when 

 carrying a single body, is united to it at a sharp angle with 

 the longer axis of the latter (fig. 24^). 



Fissigemmation. — This is the only process of reproduction 

 which has been observed. Several instances of this kind were 

 partially followed through in an incidental way, and two com- 

 plete courses were carefully noted and drawn within a half- 

 hour of each other. The set of figm-es 13, 15, 17, 19, 21 relate 

 to one individual, and figures 11, 12, 14, 16, 18, 20, 22 

 to another belonging to the same colony. The rate of pro- 

 gress of the former when the drawings were made was not 

 noted ; but that of the latter set was observed in four out of 

 six of the intervals which occurred between the phases which 

 the figures represent ; and during the progressive steps of the 

 latter it was carefully recorded which of the successive stages 

 of the former filled the intervals between those of the latter ; 

 so that it can be said, in the strictest sense, that all the figm-es 

 of both sets of observations represent the phases which were 

 distinctly marked in the second series. In this way the fullest 

 illustration possible was obtained, and no point Avas left unex- 

 j^lained. The whole time occupied by the process in the se- 

 cond series w^s, forty minutes. It has already been mentioned, 

 when describing the form of the collar, that it assumes a 

 bulging campanvilate outline (fig. 11,?>) as a preparatory, pre- 

 liminary act in fissigemmation. In addition to this, it should 

 be stated that it widens inordinately at the distal end, so as to 

 exceed by one-third its normal breadth ; but before it finally 

 settles itself into this shape and proportions, it contracts and 

 expands its diameter by a peculiar sort of vibrating motion, 

 and passes through a series of changes of form which vary 

 from a funnel-shape to a narrower cylindrical outline, or from 

 either of these to a broader cylindrical proportion, — such, for 

 instance, as figm-es 9 and 10 (representing the same individual) 

 exemplify. This would appear, also, to be the time when the 

 contractile vesicles divide 5 for at no other period were they 

 observed to be more than two in number, as they are repre- 

 sented in figs. 9 and 10 {cv). 



Immediately after this preparatory sign was discovered (the 

 time being noted at 12.55 p.m.), the flagellum became unusu- 

 ally conspicuous and much thicker, and moreover it lost its 

 sigmoid flexure and assumed a perfectly straight carriage, Avith 



