190 Part I11.—Siateenth 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 Orthona that is sometimes not uncommon in 
the Firth of Forth is probably the O. s¢milis Claus, as stated by Dr. 
Giesbrecht. 
Caligus rapax is frequently found “ free-swimming ’ 
and appears to be able to adopt that mode of life at will. 
* in the estuary, 
(3.) THa VERMES. 
THE saGiTta (S. bipunctata). 
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 larvee 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 larve of round fishes, but they also attacked the 
smaller Crustacea, and were even observed to devour their own kind— 
the larger Sagttta 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. 
Nn 
i 
iso] 
Number of Records for each Month of each Year. be . 
| [= 
Three Inner Stations. Years. : oes bee 
| | : | | | ee 
| H a nS 
| 5% a NS = 5s 
| ia} 2s gS 
| i> |e] a4 E 
| 1889, Neill ar ee 
1890, reba ya" | 
1891 er Say Os alee gs 
I 1892 leases tie | 
1893, Ro pe | Ee 
1894, Escuelas 
1895, es i if ea 
Totals forthe Months,. . . | 6 (11 | 4 
