Vol. III. August, 1902. No. 



BIOLOGICAL BULLETIN. 



ABNORMALITIES IX THE CESTODE MONIEZIA 



EXPANSA. III. 



{Continued.} 



3. ORIGIN OF THE ABNORMALITIES. 



The preceding description has rendered it evident that the pro- 

 cess of proglottid-formation begins deep within the body and only 

 gradually becomes visible on the surface. The external features 

 of the proglottids, their contours and the furrows which appear 

 between them are only indications of the localized growth that 

 has taken place within the body. Since the primary region of 

 proglottid-formation is the central parenchyma, and the process 

 extends only secondarily to the peripheral parenchyma, it is the- 

 oretically possible that a proglottid might be formed in the cen- 

 tral parenchyma without becoming visible on the surface as an 

 area of localized growth bounded by furrows. There is some 

 evidence that such a condition occasionally exists. Its discussion 

 is postponed to a later section of this paper. In general, how- 

 ever, the furrows and their external features are simply the visible 

 signs of internal processes of certain kinds and intensities. This 

 being the case, variations in form and structure of the proglottid 

 are the consequence of variation in the formative processes. 



(a) Variation in Form of Proglottids. 



The division of the variations into two groups, non-spiral and 

 spiral variations, which was adopted in Parts I. and II., is retained 

 here for convenience. The imperfect or partial proglottids are 

 considered first as showing the simpler forms of variation. A 

 study of the abnormalities of this group shows very clearly that 

 all are simply incompletely developed proglottids, either fused 

 with others or separated from them by furrows. 



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