158 CHILD. 



tion of the organs occurs in normal proglottids. These appear 

 to be extreme cases of adaptation in growth to abnormal con- 

 ditions. 



The inter-proglotticlal glands show numerous departures from 

 the typical arrangement and these variations are very closely 

 correlated with the form-variation of the proglottids. The inter- 

 proglotticlal glands lie along the posterior border of each pro- 

 glotticl just anterior to the furrow and open into the deepest part 

 of the latter. They are absent near the margins of the body. 

 In general the glands appear wherever even a small portion of a 

 furrow extends beyond the marginal region in which they are 

 never found. The glands never appear except in connection 

 with a furrow, and they appear only along furrows which are 

 transverse or nearly so. In one case shown in Fig. 38 (Pt. II.) the 

 furrow becomes oblique, but the glands tend to continue in a trans- 

 verse row, and at the anterior end of the oblique portion lie at 

 some distance from the furrow and are connected with it by long 

 ducts, while at the posterior end one gland lies posterior to the 

 furrow instead of in its normal position anterior to it. With 

 respect to this case the suggestion was made on page 283, Part 

 II., that the rows of glands may coincide with the proglottidal 

 boundaries while the oblique portion of the furrow does not. 

 The glands tend to form along the boundaries but apparently do 

 not form at all unless a furrow is present. 



The numerous variations which have formed the subject of this 

 paper have demonstrated very clearly the close relation between 

 form and structure. It remains for us to consider whether the 

 variations in structure are the result of the form-variations or 

 whether some common cause underlies both. 



The organs of the proglottid appear considerably later than 

 the proglottid itself. If variations in their form and arrangement 

 are due to the same causes as the variations in form of the pro- 

 glottid, these causes must be active after the formation of the 

 proglottid and must affect the development of the organ in such 

 a way as to cause an apparent adaptation to the form of pro- 

 glottid. 



The natural and obvious conclusion is, I think, that the devel- 

 opment of the proglottidal organs must depend upon the devel- 



