NOTES ON TELEOSTEAN OVA AND LARVAE. 25 



occasionally recorded in each year for the months April, May, and 

 June. The difficulty, if not impossibility, of distinguishing the egg of 

 Z. unimacuhdus by its dimensions may be seen by a comparison of 

 measurements of the eggs of this species, which are definitely known 

 from having been obtained from ripe females (•92--93 mm. for un- 

 fertilized, and -QO-'OD mm. with oil-globule -IG-'IS mm. for fertilized 

 ova *) with Column II in the above list. There is indeed one egg 

 (marked with a ?) in the above series which I had some ground for 

 regarding as possibly Z. unimacidatus. This was taken on the 20th 

 April in Cawsand Bay. Unfortunately my recorded observations of 

 this egg and the subsequent larva are very meagre. Just before the 

 outgrowth of the caudal rudiment there was no pigment whatever on 

 the embryo. The larva, which hatched out on the 24th April, had a 

 length within the first few hours of larval life of 2-4 mm., the pre-anal 

 length being I'O? mm. This agrees almost exactly with Holt's newly 

 hatched specimen from an artificially fertilized egg of Z. nnimacu- 

 lo.tv.s (lie, p. 46, and llf. Fig. 89). My brief notes upon the larva state 

 that yellow was the predominant pigment, occurring in moderate-sized 

 round and stellate chromatophores over body, yolk-sac and unpaired 

 fins, except at the posterior extremity of the latter. Along the margin 

 of the unpaired fins the pigment was dendritic. Black pigment 

 consisted of numerous very fine dots, scattered with the yellow all over 

 the body, fins, and yolk-sac. However, on the 27th the pigmentation 

 had assumed the same form, which I found at the same stage in the 

 other larvae hatched from the larger group of Top-knot eggs and 

 which I regard as typical of Z.puMctatus. Its identity with Z. vnimacu- 

 latus, therefore, can be based only upon the dimensions of the egg and 

 newly hatched larva, for which comparison there is still too little 

 material. Of course there is the possibility of a close resemblance 

 between the pigmentation of the later vitelligerous larval forms of the 

 two species. 



It will be noticed that my above lists indicate a somewhat different 

 period for the occurrence of the two groups of eggs, Group I 

 {Z. norvegicus) being taken from 19th April to 28th June, and 

 Group II {Z. puiictatus) from Htli February to 24th May. This 

 ditierence is, however, probably more apparent than real, for before 

 April I was not able to get any samples from further seaward than 

 the entrances to Plymouth Sound, which would leave the habitat of 

 Z. norve;jicwi neglected for the commencement of the season. 



I may now give a more detailed account of the characters and 

 especially tlie pigmentation of the two undoubtedly occurring species. 



* Cf. Holt, lid, p. 128. 



