250 ANIMAL PARASITES AND MESSMATES. 



a long worm, to which I have given the name of 

 Filaroides mustelarum. It usually forms a little sac, 

 which resembles a tubercle. Many individuals of 

 different sexes, wound round each other, are so closely 

 tied together that they can with difficulty be separated. 

 They resemble a ball of cotton. This filaroid sometimes 

 gets into the frontal sinus, and mechanically destroys 

 a part of its osseous walls, so that the skull is pierced, 

 by a hole above the frontal sinus. Dr. Weyenberg made 

 this observation. 



It is probable that other species oi Mustela will 

 present the same phenomena, for the skulls of this 

 animal are often to be found perforated above the 

 orbital cavity. 



The Ollulanus tricuspis is a worm which lives in the 

 walls of the stomach of cats ; it is viviparous, and the 

 young ones sometimes wander into the muscles of their 

 host. But the natural course of things is that the 

 young are evacuated with the feces, and that these 

 dejecta, according to all probability, form part of the 

 food of mice, and pass with them into the cat. It is 

 to be hoped that Leuckart will soon put this migration 

 out of doubt by a decisive experiment, and will prove 

 that the mouse serves as a vehicle for three different 

 worms, the Cysticercus, the Spiroptera obtusa, and the 

 Ollulanus tricuspis. 



Many nematodes lodge in the substance of the walls 

 of the gizzard of birds. In the large goosander we have 

 found one which has round its head four blades, crossing 

 each other, toothed on the concave side. We have given 

 the name of Ascaracantha tenuis to this worm. It has 

 very small eggs. The Trichosomum crassicauda is a 



