494 ON THE DEVELOPMENT OF DERMATOBIA HOMINIS. 



color and translucent appearance. These hooks are very regularly arranged in lines 

 parallel to the length of the body. The posterior margin of this somite is invaginated 

 more deeply on the ventral line than on the dorsal, which seems to be connected with 

 its varied width as noted above. But the entire circumference is turned back within 

 itself so as to form a complete collar, from within which the succeeding somite pro- 

 trudes. The denticles are continued over the margin and occur on the infolded region. 

 The groove formed by this infolding is not deep, measuring only about 30 to 50 micra 

 on the mid-dorsal line, but decidedly more on the mid-ventral. No doubt it is also 

 the greater depth of the groove in the ventral region that tilts the succeeding somite 

 ventrad at an angle with that just described, as is shown in the figure. 



Somite XI. The ultimate somite may evidently be retracted within the penul- 

 timate to a considerable extent, but in this specimen it was in a state of almost com- 

 plete eversion. It shows two very distinct regions; a proximal portion of lesser 

 caliber and with a smooth wall and a distal inflated region which is covered with 

 spines like those of the penultimate somite, but somewhat more thickly set. 



The smooth region is of uniform caliber throughout and is connected anteriorly 

 with the inturned margin of the tenth somite. The distal inflated region has much 

 the form of the glans penis, consisting of a uniformly rounded unbroken dorsal por- 

 tion and two la tero- ventral lobes separated by a shallow median furrow. Internally 

 one may distinguish musculi retractores attached to the inner face of the posterior 

 surface. 



A view of the terminal aspect of the somite discloses the anal orifice as a trans- 

 verse crescentic slit near the ventral margin, and just dorsal to it and near the median 

 line the two small stigmata. Each stigmal field appears as a group of two fimbriated 

 slots, set closely together and connecting with an elongated subjacent cylinder, with 

 heavy chitinous walls, chestnut-brown in color, in the alcoholic specimen. The 

 cylinder extends back through this last segment and at its anterior limit connects 

 with the characteristic spiral walled tracheae of the larva. 



The larva just described agrees in all essential particulars with that discussed 

 by Blanchard ('92, p. 136) under the name of ver macaque. The armature of the 

 first four somites is described here for the first time, as also the morphological identity 

 of the various hooks in contrast to the previous view which regarded those of the first 

 to fourth somites as spinules. The observation of Brauer is partly confirmed, that 

 a complete circle of smaller hooks occurs at the anterior margin of the fourth somite 

 comparable to those of the posterior half circle save in size. This is the row noted 

 above as the forerunner of the prominent row in the corresponding position on the 

 fifth somite. No previous description of the lett t~v\o tcnhes Its Icfn accmfcte, 



