The Nautilus. 



Vol.. XXIII. JULY, 1909. No. 8. 



A 8PBIN0 COLLECTING TBIP. 



Notes on Hew England NudibrancliB II. 



BT FRANCIS N. BA.LCH. 



In a recent number of the "Nautilus"' I recorded two occur- 

 rences of nudibranchs at Cobasset, Mass., indicating marked local 

 condensation of the partly grown Eolid population during the time 

 of a supposed autumn migration of the year's brood to deeper water?. 



The condensation of adults at the breeding season is of quite a 

 different order and much more familiar. The supposition is that 

 the year's adults migrate from deep water to the shore, there to 

 spend a brief mating season, spawn, and (for the most part) die. It is 

 well known that early spring is the breeding season for most of the 

 species, while others appear to select late autumn or winter — facts 

 which go far to explain our woeful ignorance of this group in this 

 country. At times, in other countries, these mating forms have been 

 found abundant and gregarious to such an extent as to justify the 

 expression " swarming " for the habit.' 



iVol. xxii, No. 2, June, 1908, pp. 13-16. "Two interesting New England 

 Nudibranch Records." The subtitle " Notes on New England Nudibranchs. I." 

 was accidentally omitted by the printer. P. 15, top line, after word "and" 

 insert "T." For other errata see Nautilus, xxii. No. 6, Oct., 1908, p. 60. 



'I use the term "swarming" in this paper to indicate a distinct gathering 

 together, in relatively great abundance, for breeding. 



Eliot ("On some Nudibranchs from East Africa and Zanzibar." Pt. V.; P. Z. S., 

 1904, ii, p. 87) furnishes a description of such a "swarming" of Trevelyana crocea, 



