34 EARLY STAGES OF TEREBRATULINA. 



were performed on many living adult speciiriens, yet in no case was the slightest evidence 

 of an anal outlet observed. 



Fig. 25 represents a stage but slightly advanced from fig. 24. The cirri are more nu- 

 merous, but still spring from a circular lophophore. 



Fig. 27, plate ii, represents a considerably advanced stage, in which the lophophore, 

 before circular, has rapidly assumed its hippocrepian character ; rapidly, — since forms 

 nearly of the same size show no marked indications of change, for in one example we 

 may have a circular lophophore, or one showing but slight indentation, while in another 

 example, hardly differing in size, we have the lateral processes well advanced in develop- 

 ment. It is possible that we may have here a feature observed by Fritz Miiller in 

 the young Discbia described by him ; he mentions the remarkable fact of having re- 

 peatedly captured free swimming young which had evidently advanced further in their 

 development than the oldest of those which had already fixed themselves. It will be 

 noticed that in this stage (fig. 27) the cirri stand erect upon the arms, that is pointing 

 towards the anterior margin of the shell, and that the arms are not deflected. This 

 stage of the lophophore vividly recalls the hippocrepian forms among the Polyzoa, such 

 as PhimafeUa, Cristatella, Lojjhopus and others. 



The liver now shows its adult characters in having its ramified caeca separated, and not 

 adhering by their walls in one mass. In this early condition it resembles the liver of 

 Thecidium, as described and figured by Lacaze-Duthiers. 



Fig. 28 represents a stage where the arms become deflected ; as yet no central process 

 of the lophophore is developed ; the mouth is very large, and that margin of it not bear- 

 ing cirri is very pliant in its movements. 



In the next stage (fig. 29) the ai'ms are more deflected and make a sharper curve in 

 their approach together, and the central process of the lophophore is indicated by that 

 portion forming the base of the inner curve, developing into two prominences. The free 

 lip is seen in irregular curves, and these changed with every movement of the parts. 



Fig. 30 represents a slightly more advanced stage, where the central processes of the 

 lophophore are more developed. The free lip is here seen thrown broadly back, disclosing 

 a capacious mouth, within which are seen two blunt projections, though in another view of 

 the mouth (fig. 31) only one projection was observed. The free lip seemed to perform 

 all the functions pertaining to the epistome in the higher Polyzoa, and we find it on the 

 inner bend of the arms, as in the Polyzoa, though not occupying the same homological 

 position in regard to the flexture of the intestine. It will be noticesd that in all these stages 

 the cirri are comparatively thick. 



In the stage represented by fig. 32, the cirri become more attenuated and increase rap- 

 idly in number ; the central process is more advanced, though not yet thrown into a 

 vertical spiral, as in the adult, and the mouth has lost the broad reflected character of 

 the lip, which it possessed in the earlier stages, though the free lip has yet considerable 

 pliancy, as seen in figs. 33 and 34, where other views of the same mouth are presented. 

 For the first time now appears another adult character, in the apparent decrease in the 

 length of those cirri in the median line of the mouth. 



In figs. 35, 36 and 37, difterent aspects of the mouth of an adult individual are shown; 

 figs. 35 and 36 representing the outline of the mouth alone, while in fig. 37 the cirri 

 are shown. In these three views the oral tubercle {ot), as it may be called, is strongly 



