M. Lespea on a Nematoid Worm, parasitic upon Termites. 889 



Isakis migrans (mihi). 



Corpus fusiforme, album: longit. maris I'S mill., foeminse 2'5 mill. 



Ovula elliptica : longit. 0'06 mill. ; lat. 0*04 mill. 

 Individua juniora, orgaiiis genitalibus nuUis (e corpore Tei'mitum) : 



longit. fere 0*3, 0*4, usque ad 0*8 mill. 



The adult males and females of this species are common in 

 the earth of the two nests. They presented the remarkable 

 property of being capable of being recalled to life after com- 

 plete desiccation for more than a month. The males are rather 

 less abundant than the females. 



In these little creatures we may perfectly distinguish the 

 digestive tube, which commences with a muscular pharynx, 

 followed by an intestine Avhich is straight in the male, and twisted 

 into a spiral in the female. The former presents a slight tubercle 

 a little above the tail ; in the corresponding part we see the two 

 spicules of 0'05 mill, in length, and the sheath of 002 mill, 

 which is placed below. The generative orifice of the female is 

 placed about the middle of its length ; by transmitted light we 

 see a great number of eggs filling the body. 



With these animals I found an immense number of free eggs 

 in different stages of development. Those furthest advanced con- 

 tained an extremely mobile embryo. Some of these escaped, but 

 there was still a gap between the young individuals and the adult 

 or nearly adult forms. To supply this it is sufficient to dissect 

 a Termite of the infested nest, when we find in the abdomen, 

 around the intestine, but never in its interior, some Nematoid 

 worms, very short and slender when compared with the adults ; 

 they are in different stages of development, but the generative 

 organs are always v/anting. I found from one to six of them, 

 but only in individuals of a certain size (workers, soldiers, 

 nymphs). All my observations were made at the beginning 

 of May, and in the second nest I verified them in June. The 

 infested insects soon languish and at last die ; . if they are then 

 examined, the developed Nematoid worms are seen issuing from 

 their bodies, which are becoming putrefied. 



From these facts I think that all naturalists will admit with 

 me, that the parasite of which I have just given the history, 

 acquires its generative organs and propagates in moist earth; 

 that the young penetrate into the bodies of the Termites, be- 

 come developed there, finally destroy their victim, and then 

 escape to complete their growth. 



The study of the probably numerous worms which have been 

 united under the name of Filaria of Insects, was commenced by 

 the remarkable work of Von Siebold upon Mermis albicans. 



