io8 



CHILD. 



FIG. 59. 



peripheral parenchyma-nuclei, though few, are grouped in the 

 proglottids. 



Now the proglottid is completely established as a localized 



region of growth. Later changes which 

 occur lead to some alteration in the shape 

 and proportions of various parts and to 

 the differentiation of various organs 

 within the proglottid. 



In some Cestodes, including Moniczia, 

 . the longitudinal nerve-cords are con- 

 nected by a series of transverse prog- 

 lottidal commissures and other proglot- 

 tidal nerves are also present. The de- 

 velopment of this proglottidal nervous 

 system has been investigated but little, 

 although it is certainly a field of considerable interest. The 

 time at which the nerves appear, their relation to the formation 

 of other parts of the proglottid and themanner of their differen- 

 tiation are all difficult but important problems. 



Tower ('oo) has described and figured the origin of the trans- 

 verse commissures in the neck-region of Moniezia (Fig. I, Taf. 

 21). Mr. Tower has had the kindness to inform me personally 

 that the folds along the margins of the neck in this figure are not 

 intended to represent the outlines of proglottids but are merely 

 the folds resulting from contraction. He finds that the transverse 

 commissures begin to appear before the proglottids are distinct, 

 but he has not been able to discover any great degree of regular- 

 ity in the order of their appearance. The first traces of these 

 commissures appear almost immediately behind the scolex, but 

 their formation is not completed until the stage where the pro- 

 glottids begin to be visible. It is possible, as Tower himseli 

 admits, that further study might show a much greater regularity 

 in the development of these commissures. 



The point in Tower's figure where the first traces of the com- 

 missures appear is certainly far anterior to the region in which 

 the proglottids become distinct, /. c., the commissures are appar- 

 ently the first of all the proglottidal structures to appear. 



The study of the neck-region of Monicrjia brings to light a 



