THE ANNULOSE TYPE. 605 



[Some memoranda bearing on the question here discussed, 

 mislaid at the time when the chapter dealing with it was revised, 

 have been discovered in time for utilization in this appendix.] 



One of my critics says : — 



" You have overstated the case in your favour : the alimentary canaf does 

 not, as you suggest, show a segmentation corresponding to that of the other 

 organs "in Annelida. Either it is a simple uniform tube, or else its differ- 

 entiations (pharynx, oesophagus, crop, intestine) are quite independent of 

 the repetition of the somites." 



In presence of statements made in works of authority, this objec- 

 tion greatly surprises me. I meet with the descriptive word 

 " moniliform " applied to the intestine in some Annelids, and 

 then in the Text-book of Claus, translated and edited by 

 Sedgwick, it is said, concerning the alimentary canal in the 

 Annelida : — 



" This is followed by the gastric region of the gut, which occupies the 

 greatest portion of the length of the body, and is either regularly con- 

 stricted in correspondence with the segments, or possesses lateral diverti- 

 cula." (P. 365.) 



And again on p. 369 it is said : — 



"The intestine usually preserves the same structure in its entire length 

 and is divided by regular constrictions into a number of divisions or 

 chambers, which correspond to the segments and dilate again into lateral 

 diverticula and caeca." 



The alimentary canal thus presents the segmental character as 

 clearly as consists with fulfilment of its function. If the suc- 

 cessive segments are cooperating units of a compound animal 

 having but one mouth, then, necessarily, the gut cannot be com- 

 pletely cut into parts, each answering to a segment, for there 

 could be, in that case, no passage for the food. If the portion of 

 the intestine belonging to each segment has a conspicuous dila- 

 tation, or has a caecum on each side, it exhibits the segmental 

 character as much as the physical requirements permit. So far 

 from being at variance with the hypothesis, its structure exhibits 

 a verification of it. 



The next objection runs as follows: — 



u Then, again, the ovaries and testes do not exhibit a corresponding seg- 

 mentation. When it is allowable to speak of ovary or testis at all as in 

 Lumbricus, we find that in the case of both organs we have at most two 

 pairs." 



It seems to me that the distribution of the generative organs in 

 a comparatively-developed member of the Annelid type, is not the 

 question. We have to ask what it is in undeveloped members of 

 that type. Among them the repetition of generative parts is in 

 some cases just what the theory implies. Thus in Claus I read : — 

 11 In the marine Chcetopoda, the ova or spermatozoa originate on 

 the body-wall from cells of the peritoneal membrane, either in 



