20 



EINAR LEA. 



[REP. OF THE "MICHAEL SARS" NORTH 



larvae in question, but as the frequency-curve in regard 

 to the number of segments takes the usual form, and my 

 suspicions were otherwise unsupported, I abandoned 

 this idea. 



Looking at the matter from a biological point of 

 view, we cannot help wondering at the great difference 

 in size and development of the various individuals. For 

 instance, comparing no. 1 with no. 20 we cannot doubt 

 that the latter is considerably older than the former, but 

 grouping the individuals according to length, there is 

 hardly anything on which to found the supposition that 



Fig. 15. Head of a large larva of Conger mystax. 10 /i. 



there are two or more distinct groups. The table shows 

 that nearly all the individuals differ in length, but it is 

 only between nos. 1 and 2 that there is any great diffe- 

 rence, the rest increasing gradually in length. 



This phenomenon can hardly be casual, seeing that 

 most of the individuals were taken in the same day at 

 the same station, and we must conclude that individuals 

 differing in size and development existed in the very 

 same locality. In this respect there is a great difference 

 between these larvae and the larvae of Conger balearicus, 

 which included individuals practically speaking at the same 

 stage of development (the individuals group themselves 

 round an average in the manner usual for biological 

 variation). We must not, however, draw too comprehensive 

 conclusions from the catches, and it is difficult to decide 

 whether this difference, so conspicuous in our material, 

 is dependent upon differences in the biology of the species 

 in question (for instance a greater or less extension of 

 the spawning time). Our catches can hardly be compared 

 with Schmidt's catches in the Mediterranean, for in his 

 paper (29) he states quite generally that "the occurrence 



of the larvae shows that Conger mystax spawns later in 

 the year than Conger vulgaris, i. e. later in summer and 

 autumn, at which times of the year the smallest stages 

 are found, and it is possible that this species spawns a 

 little nearer the coast than Conger vulgaris". 



As to the distribution of this species Schmidt believes 



that it belongs to the Mediterranean, his investigations 



having proved that the larvae occur commonly in the 



Mediterranean, while outside this sea only a few specimens 



have been taken in the Atlantic not far from Gibraltar. 



The "Michael Sars" stations where the larvae in 



question were caught are situated near the coast of 



Morocco, about seven degrees of latitude to the south 



of Gibraltar. Considering this distance, and the early 



stages of the smaller larvae, I am of opinion that it is 



improbable that they came from the Mediterranean, the 



more so as the adult animals have been caught in the 



eastern Atlantic (Jordan and Everman). It seems to me 



more reasonable to suppose that the distribution of this 



species is dependent on certain external conditions to 



be found in the Mediterranean and in the eastern 



Atlantic only, for it is an established fact that the larvae 



have hitherto been found only in these localities. 



Our material gives valuable information regarding 

 the vertical distribution of the larvae, for the table 

 shows that 



2 larvae were taken at a depth of 100 metres 



r ' » i> i) »i - -l £>o „ 



1 larva was „ - - „ - 1000 



As nets were dragged at depths of 0, 50, 100, 150, 

 250, and 400 metres at Stat. 42, where most of the larvae 

 were caught, there is little doubt that at this place the 

 larvae occurred in greatest abundance between 100 and 

 150 metres. 



Note. — I was somewhat in doubt whether a larva 

 from Stat. 58 (no. 21 in the table) belonged to Conger 

 mystax or to some closely allied species, because of its 

 size (length 17 cm), which far exceeds the general size 

 of the larvae of this species, 1 ) and because the head is 

 relatively smaller than in the other larvae entered in the 

 table, but as it corresponds perfectly to the larvae of C. 

 mystax in all the most essential characters, I have con- 

 sidered it right to avoid setting up a new species. The 

 number of segments, the number of rays in the caudal 

 fin, the number of rays in the pectoral fin (10 to 12) and 

 in the anal fin (160 to 175), agree with those on the 

 other individuals. 



*) In regard to this matter Dr. Jons. Schmidt says (29): "The full-grown larvae of the Conger-species mentioned (C. vulg. 

 balearicus, mystax) differ in regard to size C. balearicus has the largest larva (ca. 20 cm.), C. mystax the smallest (ca. 13 cm.), whilst the larva 

 of C. vulgaris may attain a length of ca. 16 cm. 



