DAVAINEA MADAGASCARIENSIS. 171 



It is very much elongated, measuring from 50 to 64 /i long by 19 to 23 |U, broad. 

 One end is bluntly rounded, the other rather more tapering. 



Tlie oiichosphere is circular or nearly so a-nd measures 14 to 15 At in diameter. 

 On one side is a slight, blunt, flat-topped eminence bearing the three pairs of 

 nearly straight hooklets, the latter being from 4 to 5 /^ long. Usually the 

 onchosphere lies near the middle of the long diameter of the egg, but it is 

 occasionally displaced to a position near one end. 



Other authors who have studied the egg of Davainea madagasoariensis (Da- 

 vaine, Leuckart) describe the inner shell as closely enveloping the embryo. Such 

 would be the interpretation in the present case from the appearance of the egg 

 in the mounted specimens, but from a study of the eggs in digested segments it 

 seems quite clear that the inner shell is normally of the form described above 

 and pictured in figure 4. 



SIGNIFICANCE OP THE PRESENT FINDING. 



The first three findings of D. madagascariensis in the islands off 

 Madagascar (in 1867, 1873, and 1891) might well have been taken to 

 indicate a possibly narrow range of distribution in that locality, al- 

 though one of Grenet's cases had come from the Antilles five months 

 previously. Krabbe's case at Bangkok in 1891 at once widened this 

 range greatly and suggested the possibility of a rather extensive distri- 

 bution. Daniels's case in British Guiana in 1895, as pointed out by 

 Blanchard, opened a new era in the history of the parasite and in- 

 dicated a general distribution of the species throughout the Tropics. 

 Still, after a lapse of fourteen years, the parasite was not again encoim- 

 tered until Andrews's case in the Philippine Islands completed the belt 

 of distribution around the world and practically gave final proof of the 

 more or less general tropical distribution of the parasite. 



From the viewpoint of age distribution it is noteworthy that while 

 six of the eight cases reported in the first four findings of D. madagas- 

 cariensis were young children, the age of the other two not being stated, 

 the last two cases (Daniels's and Andrews's) were adults. 



Another interesting point is the apparent relation between the in- 

 cidence of the infection and maritime surroundings. The first seven 

 cases were insular and all ten have been found at port towns. In ad- 

 dition, two of Chevreau's patients had arrived by ship two months and 

 five months previously, and Krabbe's case, the son of a sea captain, was 

 said to dwell on his father's vessel. The significance of this seeming 

 relationship is problematical. It might mean that the intermediate 

 host is some animal of wide distribution in the Tropics and particularly 

 infesting such situations as ships and docks, for example, the cockroach 

 (Periplaneta orientalis) as Blanchard has suggested. On the other hand, 

 further investigation may show the parasite to exist in the interior as 

 well. Heretofore, there has been comparatively little opportunity for 

 investigation in such regions. If this were the case, the apparent rela- 

 tion between the infection and shipping would, in part at least, lose 



