STUDIES ox THE ECTOPARASITIC TREMATODES OP JAPAX. I79 



occasion I kept a few specimens of ilf. caudata jaat taken from a very 

 fresh fish, on a glass slide covered with sea-water, these executed 

 what Haswell calls "looping" movements (spannende Bewegung) 

 like those of the leech. The worm, namely, fii'st attached its anterior 

 end to the slide, apparently by means of the anterior suckers, and 

 dragging after it the hinder part of its body, attached the caudal disc 

 close up to the anterior end by means of the posterior suckers, the 

 body in the meanwhile being folded on itself on the ventral side so 

 as to form a loop ; the -worm then let go the anterior end and stretch- 

 ing its body, again attached it to the slide, detaching at the same time 

 the posterior sucker's, which were then again brought close up to the 

 anterior end, and so on. The looping movement is slow in Micr'oco- 

 tyle, but in Monocotyle it is very rapid and enei'getic and is just like 

 that of an excited leech. The worms moved quite rapidly while on 

 the host, but when I transferred them to a watch-glass filled with sea- 

 water, they at once began wandering about so quickly that each 

 looping movement could only just be distinguished, and now and' then 

 they groped about with the anterior extremity of their body, thus show- 

 ing apparently signs of surprise. The posterior sucker of this worm, 

 containing as it does the striped muscular fibres already described, 

 adheres very strongly to external objects — not only to the surface of the 

 mouth-cavity but also to a smooth surface such as that of the watch- 

 glass. Tristomum siiiuatum executes locomotion quite rapidly but 

 still much more slowly than Monocotyle. The comparatively small 

 posterior sucker of this worm is capable of adheriiig very tightly to 

 the surface of the gill. When the worm advances its anterior suckers 

 to attach thein to the substratum, it stretches out its body to such an 

 extent that it becomes much elongated and its breadth is reduced to 

 about one-third its length. Besides the looping movement which all 

 the three species above mentioned are able to execute, I have also 



