190 



Part III. — Sixteenth Annual Report 



Dermatomyzon nigripes is also only once mentioned in the tow-net lists 

 for the selected stations. 



Monstrilla sp. The most curious of the pelagic Copepods is the 

 Monstrilla. Two species — M. helgolandica and M. rigida — have been 

 captured in the estuary. In swimming it differs from the usual Copepod 

 habit by keeping its antennules straight out in front, instead of holding 

 them at right angles. 



Oithona sp. The Oithona that is sometimes not uncommon in 

 the Firth of Forth is probably the 0. similis Claus, as stated by Dr. 

 Giesbrecht. 



Caligus rapax is frequently found " free-swimming " in the estuary, 

 and appears to be able to adopt that mode of life at will. 



(3.) The Vermes. 



THE SAGITTA (S. MpUflCtata). 



Leaving the Copepoda, I now pass on to consider the distribution of 

 the Sagitta. A glance through the lists of pelagic invertebrates which 

 form part of the trawling records shows that the Sagitta forms an item of 

 considerable importance amongst the various objects collected by the tow- 

 nets. Moreover, when the voracity of these curious organisms is taken 

 into account, it is evident that the vast swarms of them that occasionally 

 visit our shores must form a, destructive agency of no mean order, and 

 especially if in the vicinity of their swarms fish larvae happen to be more 

 or less common. It has been clearly proved that Sagitta prey to a con- 

 siderable extent on larval and post-larval fishes — chiefly round fishes. 

 This habit was observed by me several years ago, and before much atten- 

 tion had been given to it otherwise ; and it was found that the Sagitta 

 not only preyed on the larva? of round fishes, but they also attacked the 

 smaller Crustacea, and were even observed to devour their own kind — 

 the larger Sagitta devouring the smaller. 



The distribution of the Sagitta in the Firth of Forth during the seven 

 years will be best seen by a reference to the annexed Table. 



Table X., showing the Distribution of Sagitta, as indicated by the Tow- 

 net Records for the Years, Months, and Stations. 



/ 

 Three Inner Stations. 



Years. 



Number of Records for each Month of each Year. 



73 



u 



aj 

 03 . 



Hg 



03 O 



Si 



CO 3 



o 

 H 



S 



9 

 13 

 10 

 13 



7 



c 



1-5 



03 



o 



3 



< 





03* 



c 



1-5 





< 





4J 

 O 



O 



> 

 o 



d 



P 

 1 



2 

 1 



2 

 2 



I. 



1889, . 



1890, . 



1891, . 



1892, . 



1893, . 



1894, . 

 189.5, . 



1 



_ 



1 

 1 



2 

 1 



2 

 2 



1 



1 



2 

 2 

 1 



2 

 1 

 1 



- 

 •) 

 1 

 1 

 1 

 1 



2 

 2 

 1 



1 



1 



2 



1 



1 1 



l ; l 



i 



l 



i l 

 l 



1 

 1 



1 



1 



1 

 1 



1 



1 

 1 



L 

 1 

 •2 



Totals for the Months, . 



6 i 11 



i 



4 



6 



6 1 4 



4 j 4 



3 i 4 



1 



6 



8 



66 



