112 DR. J. STEPHENSON ON THE MORPHOLOGY, CLASSIFICATION, 



of the nerve cord, almost at the level of the anterior border of 

 the crop*. At 1, two small morulse were visible, attached to 

 strands in the dorsal region of the body-cavity, and moving with 

 the strands. At 2, ventrally situated at the level of the hinder 

 part of the stomach, were a nnmber of morulae of large size, of 

 which one or more were quite free. At 3 were a considerable 

 number, apparently fixed to strands. At 4, in the next indi- 

 vidual, were a large number of morulas behind the developing 

 pharynx and oesophagus, all seeming fixed to numerous strands 

 in this region ; this attachment seemed also qiiite beyond doubt 

 on subsequent examination in cedar oil. At 5 -were seen three 

 morul?e on a level with the anterior part of the crop, on strands, 

 to which they remained attached even on moderately violent 

 movements of the animal under the coverslip ; one or two others 

 in this component of the chain were quite free. At 6 were two 

 morulse, also apparently attached to strands ; and this was con- 

 firmed by subsequent examination in cedar oil under the immer- 

 sion lens. At 7 were a number, one showing commencing 

 differentiation into central (granular) and peripheral (cellular) 

 parts ; two at least of these, well seen, were obviously, one would 

 say, fixed, and not merely entangled in the strands. 



In the above example it happens that all the morulas in course 

 of development were situated on sti'ands in the body-cavity; and 

 such strands appear to be the commonest site of their pro- 

 duction. I have repeatedly seen the morula; on the strands keep 

 their attachment in spite of the animal's movements and conse- 

 quent swaying of the strands to and fro — indeed, I have no note 

 of ever seeing them shaken off. These strands are frequently 

 situated in the anterior region of 3?oung individuals, towards the 

 fi'ont end or about the middle of what will be the crop, sometimes 

 behind its middle, or behind the stomach ; as exemplified above, 

 they may be either dorsal or ventral to the alimentary tube ; not 

 infrequently they are in the angle between the strand and the 

 body-wall, and might be described with equal correctness as 

 ai'ising from the parietes. 



The greatest production of morulas may not be in the parent 

 animal — -perhaps seldom is so. I have, for example, noted the 

 production as being most active in the individual behind the 

 primary fission zone, and in the one succeeding this, and as being 

 small in the anterior half of the chain. It will be understood 

 that besides the fixed and not fully-developed morulas, there are 

 other larger ones which float freely in the body-cavity. 



A curious and perhaps pathological condition was met with in 

 some specimens which had been in a tube in the laboratory for a 



* The alimentary canal in Ghcetog aster shows a considerable degree of differentia- 

 tion ; the pharynx may be said, in this species, to occnpy the first three segments, 

 the oesophag-us the fourth, the crop the fifth to part of the seventh, the stomach 

 most of the seventh and the eighth, and the intestine (very short compared with the 

 part of the tube so called in other Naididas) the few remaining segments. 



