146 CHILD. 



with and confirm the observations discussed above, on the devel- 

 opment of the normal proglottid. 



The examination of imperfect or partial proglottids in the light 

 'of the facts gained from the study of normal proglottid-develop- 

 ment leads to the following conclusions ; the right and left halves 

 of the proglottid pass through at least the early stages of their 

 development independently ; either or both may remain incom- 

 pletely developed, as regards size, form, or distinctness, or only 

 certain parts of one or both may develop, or finally one may be 

 wholly absent. All imperfect and impartial proglottids are the 

 result of such incomplete development, and in their manifold 

 forms illustrate a great number of different combinations of the 

 various factors concerned. 



A very early stage of abnormal proglottid-formation is illus- 

 trated in Fig. 57. The dotted lines drawn through the figure 

 indicate approximately the boundaries of an abnormal region. 

 On the left side two half-proglotticls are forming, and correspond- 

 ing to these on the right is only one. In this case the growth is 

 almost wholly confined to the central parenchyma, so that fur- 

 rows on the surface are not yet present. Yet I think that there 

 can be no doubt that this region represents an early stage of a 

 condition similar to that shown in Fig. 9, for example. On the 

 other hand, the account of proglottid development has rendered 

 it evident that the zones of nuclei represented in Fig. 57 develop 

 from the lateral groups of early stages. This case forms in some 

 respects a connecting link between the observations upon normal 

 proglottid-development and the facts gained from the study of 

 older, well-developed abnormalities. It is the only case of abnor- 

 mal form observed at so early a stage. 



The spiral modifications of form were described in Part II. 

 (Child, 'oo) and include Figs. 24-37. The simplest form of 

 spiral is such as appears in Figs. 24, 25 /; and 26 (Fig. 26 is 

 reproduced as Fig. 72), viz., a single half or fractional proglottid 

 united on one surface with the proglottid posterior to it, or sepa- 

 rated by a furrow as in Fig. 24, and on the other surface with 

 the proglottid anterior to it. 



It is of course evident that such a short spiral differs only 

 slightly from a fractional proglottid of the sort which is shown in 



