MOLLUSCA OF PLYMOUTH. 449 



July 7tli. — Eight specimens taken in Cawsand Bay with the 

 bottom tQw-netj varying- in size from ^ inch to nearly \ inch when 

 completely extended. The largest individuals had seven branchial 

 plumes onlyj the largest being median and anterior. 



July 11th. — One, -^-q inch long when not fully extended (probably 

 -j^ inch when extended), dredged off the Duke Rock. I found it on 

 a colony of the compound Ascidian Fragarium elegans, and it was 

 apparently feeding upon it. 



July 24th. — One, f inch long, on a stone dredged off the Duke 

 Rock. 



August 6th. — Three, the largest just over { inch long, dredged off 

 the Duke Rock. 



August 7th. — Two, just over ^ inch in length, dredged off the 

 Eddystone in 25 — 40 fathoms, one mile south of the Hand Deeps. 



August 11th. — Eight specimens, from -j% inch to just over | inch 

 long, on stones dredged off the Duke Rock. 



August 13th. — Three specimens dredged two miles south of the 

 Mewstone, one being -f^, one f , and one -^ inch long. The first speci- 

 men possessed an unusually broad foot, which, when the animal was 

 viewed from above, extended beyond the pleuropodial frill on each 

 side. This specimen agrees, therefore, with Montagu's Doris mar- 

 ginata, and shows the probable correctness of his figure — contrary to 

 the opinion which Alder and Hancock expressed in their Monograph. 



August 18th. — One specimen, | inch long, on a stone covered with 

 encrusting polyzoa and algae, extreme low water, spring tide, east 

 end of Drake's Island. 



August 24th. — Two specimens, each -^q inch long and with eleven 

 branchial plumes, found under a stone in Bovisand Bay at low water, 

 neap tide, by Mr. M. F. Woodward. 



August 25th. — One, f in. long, dredged between Picklecombe 

 Fort and the Breakwater. 



These statistics, in conjunction with the facts concerning last 

 year's specimens, show conclusively that the eggs laid in the early 

 spring have passed through their metamorphoses, assumed the 

 specific form, and attained an average size of | inch towards the end 

 of June. The young Nudibranchs grow in size, being ^ inch in 

 length by the middle of July and f inch by the middle of August. 

 In October the average size^ is § inch, and by the end of November 

 the specimens most frequently found are nearly | of an inch in length, 

 while they may attain to maturity in December under exceptionally 

 warm conditions. 



^ This average is probably a little too bigh for the individuals wbich are still some 

 distance from the shore. On October 16th, of seven specimens dredged near the Duke 

 Rock, one was ^\ inch, one i inch, four -^ inch, and one § inch in length. 



