1893. MARINE ANIMALS. 33 



III. — A Fighting Stratagem of Palinnrus. 



The Common Crawfish {Palimmis vulgaris) ' has many points of 

 interest, and not the least curious is his plan of combat when matched 

 with a powerful antagonist. Without chelate limbs, he seems weak 

 and defenceless. One is at first inclined to commiserate this apparent 

 want of means alike of offence or defence, especially in comparison 

 with his kindred, the lobsters, armed so well with powerful seizing 

 chelae. That he had means of defence seemed probable ; but it is 

 only within the last few days that this was satisfactorily demon- 

 strated. Without any particular intention in view, we had dropped 

 a medium-sized lobster into the tank containing two large Palinnrus. 

 At first no sign was given, but in a little while we were attracted by 

 a loud noise as of a skirmish, and had an inimitable object-lesson in 

 Crawfish warfare. The larger of the two Crawfish apparently 

 resented the intrusion of the lobster, and was determined upon 

 ejection. There was a good deal of preliminary sparring, but the 

 fight which promised to be protracted ended suddenly in a most 

 unexpected manner. Making a sudden twist, the Crawfish got above 

 the lobster crosswise, and suddenly snapping his powerful tail, 

 jammed the body of his antagonist in the fold, thus impaling him on 

 the sharp downward spikes of the pleura that are such conspicuous 

 objects in a side view of Paliminis. The lobster was put quite hors de 

 combat, for his body was terribly mutilated by the sharp spines, which 

 had pierced his armour as though it were tissue-paper. Besides this 

 instance, cases are known where persons, incautiously handling 

 the Crawfish, have received wounds on the arm inflicted by similar 

 sudden flap of the tail. 



IV. — Abnormalities in Haliclyshis (Lucernaria) octoradiatus. 

 (Preliminary note.) 



This year, having occasion to examine a very large number of the 

 Lucernarian most common in these seas, viz., H. octoradiatus, I was 

 surprised to find a very large proportion to possess more or less 

 strongly-marked abnormal features. These were divisible into two 

 groups, the first where the coUeto-cystophores were malformed, the 

 second where these organs or the grouped tentacles were above or 

 below the normal number eight. 



The specimens gathered were in two lots, the one taken in 

 February and March comprising large adult individuals ^ to i in. in 

 diameter, the other collected in the beginning of June, and made up 

 of half-grown individuals, averaging half-an-inch across, but in which 

 the ova, etc., were well advanced. 



The malformed colleto-cystophores showed several interesting 

 points, but the only one I wish to dwell upon now was a common 

 case, where the summit of the organ showed very obvious homology 

 with the ordinary capitate tentacles. In many the resemblance was 



