80 THE PDR SEALS OP THE PRIBILOF ISLANDS. 



were crowded into the upper end of the large intestine. The affected part of the large intestine is 

 modified in the same way as that of the small, except that the small swellings are absent, the entire 

 affected region being greatly enlarged and very tense. 



Sometimes the walls of both small and large intestines contain small, whitish, granular bodies 

 imbedded in them. These are not egg pockets, but diseased places. 



The two sexes of the Uncinaria are easily distinguished by the diiference in size and by the 

 terminal organs of the male. The male is shorter and slenderer than the female, being about 9 

 millimeters long, and has the posterior end provided with two opposing sets of three large, inwardly 

 curved, claw-like appendages. The female is about 14 millimeters long, and the posterior end of the 

 body is conical, with a short tubular prolongation. 



A large number of females were examined with a microscope during the time from August 20 to 

 September 4. Only one of them contained no eggs. The others all contained a great number— more 

 than a hundred, iii those counted. When the worms kill a pup, they kill then. selves also. The 

 females expel some of their eggs into the intestines during the life of the pup, and then pass to the 

 exterior in the faeces. Numerous eggs may be found in the contents of both intestines by use of a 

 microscope. These are generally in the process of division, consisting of eight or ten cells. Many are 

 undivided, however. The eggs in the female worms are in the same condition. In a dead pup the 

 unlaid eggs greatly exceed in number the laid eggs present in the intestine at the time of death. 

 Therefore, by the killing of the pup, the worms kill a large proportion of their own eggs, unless the 

 latter develop in the dead pup. Some eggs were examined from a rotting pup that must have been 

 dead at least four weeks. A few were apparently decomposing, but the rest frere in various stages of 

 division. Many of the latter were placed in a drop of water on a glass slide and floated in a tight jar 

 of water to prevent desiccation, in order to learn whether they would develop further or not. A 

 hurried leaving of the island prevented the results being known. 



The embryos of Uncinaria are undoubtedly taken into the stomachs when nursing, 

 being brushed up from and with the sand by the fur of the female seals, and then 

 swallowed by the young. This supposition is corroborated by the fact previously 

 stated that few starved or starving seals contain any Uncinaria, the worst afl'ected 

 being the best nourished, many having died immediately after having eaten a hearty 

 meal. 



Out of 29 pups which had died from Uncinaria the stomach was full in 14 cases, 

 partially full in 9, and empty only in 6, and it has been suggested by Dr. T. M. Wood 

 that death may follow immediately after a full meal as a result of the eflFort of the 

 enfeebled system to digest it. 



The Uncinaria are practically confined to those rookeries where there is more or 

 less sand, and it must be remembered in this connection that many localities where 

 the ground is so plentifully strewn with rocks as to deserve the term of bowlder areas 

 contain au abundance of sand among the rocks. This is partially the case on the 

 Eeef, Gorbatch, and Northeast Point, all localities where Uncinaria abound, although 

 the headquarters of the pest seems to be on the sands of Tolstoi, Zapadni and Polovina 

 coming next. 



It is interesting to note that level, sandy areas thickly crowded with seals, on which 

 deaths from trampling would be most likely to occur, are also the areas most favorable 

 to the propagation of Uncinaria and their transmission to the young seals. 



The sandy areas are not only favorable for the retention and development of the 

 embryos of Uncinaria, but favorable to their transmission to the pups, for the reason 

 that the females in lying on or moving over the sand get more or less of it in their 

 coats, and a part of this is swallowed by the nursing pups. So much is sometimes swal- 

 lowed as to give the milk a slightly grayish cast, the milk being so thick that sand 

 does not settle in it. 



