156 ANIMAL PARASITES AND MESSMATES. 



in the bodies of the latter were eggs ready to be laid, 

 and millions of embryos of every age rolling over and 

 struggling among the full-grown worms. Is this a 

 species of worm new to science ? Is it a worm which 

 lives in freedom here, and parasitically elsewhere ? The 

 first female which presents itself allows us to answer 

 this question. It is not a parasitical worm, at least 

 under this form, because each female contains only one 

 or two eggs. Parasites have so few chances of arriving 

 at their destination, that two young ones would not be 

 sufficient. They must have hundreds or thousands, and 

 then the chances are against them. This w^orm is 

 evidently a Rhahditis, but is it that which lives in the 

 earth, or an allied species? Future observations will 

 perhaps enable us soon to reply to these questions. We 

 do not think that these creatures could have been 

 brought with the bones from the Shetland Isles; they 

 came rather from the horse-dung, and they multiplied 

 beyond measure in the spongy tissue of the bones, where 

 they found good cheer and a convenient lodging. A worm 

 very nearly allied to this exists in abundance in the 

 dung of the cow, to which our regretted colleague, the 

 Abbe E. Coemans, had directed my attention, at the 

 time when he was studying the Piloholus cristallinus. 



That which decided us to make mention of the 

 nematode of the bones, is the singular history of an 

 ascaris of the frog, whose young ones resemble their 

 parents neither in size, form, or manner of life. There 

 is one generation which can provide for themselves, and 

 is composed of males and females; and another which 

 requires assistance, and only consists of females ; unless, 

 indeed, those of the male sex are hidden among the 



