detach itself from one gill filament and attach itself to a neighboring one. 

 Many Microcotylidae with a large number of attaching clamps are practi- 

 cally devoid of the ability to transfer, although the separate clamps can 

 easily change their position. As a matter of fact, among these species the 

 adhesive glands of the posterior end are completely undeveloped and they 

 are not in a condition to attach themselves to smooth glass surfaces with 



their posterior ends. This applies to 

 the adult individuals, wnile the young 

 ones still possess attaching capability. 



The reactions of the host to 

 the attachment of monogenetic trema- 

 todes can be very different. With the 

 attachment of worms by means of 

 hooking apparatus, we often observe 

 significant injuries to the body of 

 the host. On the gills of fishes 

 strongly infected by Dactylogyridae , 

 one can easily notice numerous 

 hemorrhages and ulcerations of the 

 epithelium. It was already nnentioned 

 that during the attachment by means 

 of the discs, large round bruises and 

 swellings are formed. At the same 

 time, significant ulceration of the 

 tissues of the host also takes place in 

 serious cases of this type. The highest monogenetic trematodes which 

 attach themselves by means of clamps apparently inflict the least damage. 

 In a number of cases the irritation of the tissues of the host under the in- 

 fluence of the presence of the worms will 

 cause growth of epithelium and con- 

 necting tissue, as a result of which 

 significant swellings develop. With 

 this, anaong a number of hosts the 

 tissues will grow over and around 

 the attaching disc of the worm, and 

 among some, special growths are 

 formed on which the parasite re- 

 mains and these growths often fall 

 off carrying the worm with them, 

 and in this fashion, clear the para- 

 site from the host. We see ex- 

 amples of fixation by the tissues of 

 the host among Dactylogyrus iwanowi 



Bychowsky (Fig. 108) and Linguadactyla growths. Magnification 30 times. 

 molvae Brinkmann. The second type (According to Wunder, 1929). 



of changes of the tissues of the host 



Fig. 110. Linguadactyla molvae 

 Brinkmann, adult worm on the 

 gills of Molva dipterygia elongata 

 from the south of England (Atlantic 

 Ocean). Natural size of worm 

 about 3 mm. 



Fig. 111. Dactylogyrus vastator 

 Nybelin, adult worms on the gills 

 of the carp, forming pathological 



p. 78 



75 



