Vol. III. July* 1902. \o. 



BIOLOGICAL BULLETIN. 



ABNORMALITIES IN THE CESTODE MONIEZIA 



EXPANSA. III. 



C. M. CHILD. 



In Parts I. and II. of this paper (Child, 'oo) the various abnor- 

 malities occurring in Moniczia c.rpausa were described, in Part I. 

 those consisting of imperfect and partial proglottids and in Part 

 II. the spiral abnormalities. It now remains to determine the 

 manner in which these various abnormalities arise, and to discuss 

 the significance of the facts observed. 



As is clear from preceding descriptions, there is not the slightest 

 evidence that any of the form-variations of the proglottids appear 

 after development of the proglottid is begun. The degree of 

 differentiation of all parts of an abnormal proglottid is the same, 

 and corresponds to its position in the chain. All the various 

 kinds of form -variations occur in the youngest distinct proglottids. 

 These facts lead to the conclusion that the variations in form 

 appear at the time when the proglottid is formed ; that imperfect 

 and partial proglottids and spiral series take their origin in that 

 part of the body in which the causes that lead to the formation 

 of proglottids are at work. That is to say, variations in form are 

 the result of variations in the original formative processes, not the 

 result of modification in the form of structures already established. 



Since this is the case, the process of formation of the normal 

 proglottid may be expected to throw some light upon the factors 

 concerned in the formation of abnormalities. The first part of 

 this paper is devoted to a description of the normal method of 

 proglottid-formation. 



The figures are all semi-diagrammatic, but in the figures of 

 sections the nuclei of the parenchyma were drawn in with the 



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