22 Malformations of Ascophyllum and Desmarestia. 



the epidermal layer and a forcing asunder of the tissue beneath is observed 

 (plate VII., fig. 4), caused probably by the entrance of the nematode from 

 without ; and the space thus made is filled with a granular substance, 

 in which I believe I have found parts of the animal cut through. It is 

 difficult, however, to find the nematode in the young galls, as the cross 

 sections of the cells of the thallus bear much superficial resemblance in 

 outline to similar sections of the animals. The effect of this forcible 

 entrance of the nematode appears to be that the thallus swells up all 

 round the spot inhabited by the animal, probably caused, like gall 

 structures in general, by the stimulation of some animal secretion. I 

 have in no case found any communication between the galls along the 

 interior of the thallus, and I am therefore forced to believe that the 

 nematode attacks each affected spot separately and from outside. 



The material of Ascophyllum no do sum collected at Stonehaven shows 

 the same hollows filled with nematodes, and, as these growths appear 

 to be rather common, I imagine that Ascophyllum is a favourite resort 

 of this species of worm. I have in no instance found these malformations 

 inhabited by any other sort of animal, and only by nematodes in a fully 

 grown condition. 



As regards the nematode itself, I have sent specimens of it to 

 Dr. de Man, of Middelburg, who has very kindly examined them, and 

 pronounces the species to be new to science. We have therefore called 

 it Tylenchus fudcolus, n. sp,, and a detailed description of it with plates 

 will shortly be published by Dr. de Man, to whom I here offer my best 

 thanks for the interest he has taken in this investigation. 



I also wish to express my indebtedness to Professor King for the 

 trouble he has taken in sending me fresh material from time to time, 

 and for the interest he has shown in the work. 



Through the kindness of Mr. Batters, I have been enabled to examine 

 malformations on Desmarestia aculeata, Lam., found by him on the island 

 of Cumbrae in September of last year. The malformations in this Alga are 

 small round bodies, sometimes growing singly on a young part of the 

 thallus, sometimes grouped together on the thick stem, forming a slightly 

 raised ridge about a quarter of an inch long. In other places a lump is 

 formed in the angle of the branches, in shape somewhat like the young 

 malformations on Ascophyllum Jtodosuw, described above ; and it is in 

 these lumps that there is the greatest likelihood of finding the animal 

 which causes this growth, viz., a copepod. 



A vertical section through one of these swellings, transverse to the 

 thallus, shows that the hypertrophied tissue is composed of very closely 

 interwoven anastomosing hyphae, which somewhat resemble the ordinary 



