514 DR MASTERMAN ON THE FURTHER ANATOMY AND 



After drawing the specimen, it was removed from its mounting and sectioned, but 

 its state of preservation has prevented even the determination of the exact position of 

 these structures, whether in the rectum or the ovary, though they are more probably in 

 the latter. 



The examination of another specimen in the same collection furnished a series of 

 eggs free in the ccencecium, which were at different developmental phases, and from 

 these I have been enabled to figure at least three stages. 



Fig. 87 shows the egg contained in its capsule with a stalk of attachment, very 

 much as described by Professor M'Intosh (4), but of a more elongated outline. Fig. 88 

 shows a later stage in which the elongation is more pronounced and the egg has 

 assumed a pear-shaped outline. 



In fig. 89 a larval stage is seen, which is of some interest. A constriction has 

 appeared slightly forward of the equator and divides the body into two segments. The 

 resemblance of this larva to the early larval stage of Balanoglossus, as figured by 

 Bateson, prior to the external differentiation of the collar-segment, is very striking* 

 The presence of these larvse indicates that at any rate a certain amount of the 

 development takes place in the ccencecium, and that it may be possible to obtain 

 a series of eggs and larvse in which the early stages may be successfully followed out. 



Asexual Reproduction. 



Professor M'Intosh (4) has already given a general description of the budding 

 processes in Cephalodiscus, but a re-investigation of the subject, with plenty of good 

 material, has enabled me to work out further details. 



The buds are borne upon the pedicle, at the extreme distal extremity and upon the 

 ventral surface. The distal extremity of the pedicle is modified into a sucker, and it 

 is on the ventral border of this sucker that a pair of buds are produced. Occasionally 

 three may occur, but, at least in some cases, the presence of a third is accounted for 

 by the fact that the pedicle of a bud has commenced to bud in its turn, so that no less 

 than three generations may be in organic continuity with each other. 



Apart from this phenomenon we may say that two buds, on either side of the mid- 

 ventral line, are the rule. This arrangement is comparable to that found in the 

 creeping stolon (gymnocaulus) of Rhabdopleura, as already pointed out by Professor 

 Lankester (3). 



The pair of buds are rarely at the same stage of development ; one is often at the 

 stage with three pairs of plumes, whilst the other is a mere knob. 



The bud first appears as a small rounded protuberance of the ventral body-wall, to 

 one side of the mid-ventral line. It consists of a single layer of ectoderm and of 

 mesoderm surrounding a space which is part of the pedicular coelome. 



* Of. also the larval Phoronis, as figured by Caldwell. Quart. Journal Micros. Science, pi. ii. fi^. 3. 



