386 



Part III. — Seventh Annual Report 



important addition to the fauna of Plymouth has recently been made by 

 the discovery of Amphioxus lanceolatus in the neighbourhood. 



In the last number of the Journal of the Marine Biological Associatiou, 

 Mr J. T. Cunningham has a long paper on the ' Eeproduction and 

 Development of Teleostean Fishes occurring in the neighbourhood of 

 Plymouth/* This paper contains an account of the breeding, under 

 natural and artificial conditions of the ova of various fishes, including 

 the boar or cuckoo-fish, red gurnard, lemon-sole, common-sole, mackerel, 

 butterfly blenny, dragonet, and a variety of others taken in the tow-net. 

 A great portion of the paper is taken up with the development of the 

 lemon-sole, common-sole, and mackerel. Ova were chiefly obtained by 

 means of trawlers going to sea from Plymouth. On these voyages 

 either Mr Cunningham or the fisherman of the station usually accompanied 

 the trawler, but sometimes the ova were obtained and fertilised by the 

 fishermen themselves. In this way fertilised ova of the lemon-sole were 

 obtained in April and May, thus showing that the spawning period for 

 this species at Plymouth is during these months. The ova, in their 

 homogeneous yolk and small perivitelline space, resemble those of other 

 species of Pleuronectes and many species of Gartus. The progress of develop- 

 ment showed complete segmentation at the end of the first day, extension 

 of the blastoderm over the yolk at the end of the second day, mesoblastic 

 somites and optic vesicles at the end of the third day, and lenses, auditory 

 vesicles and pigment at the end of the fourth day. The specific gravity 

 of the ovum of the lemon-sole is 1*024, while that of the ovum of the 

 common-sole is between 1*026 and 1*027. The distinguishing features of 

 the ovum of the sole are a great number of minute oil globules arranged in 

 groups of irregular size near the edge of the blastoderm, and a layer of 

 j oik segments, forming a superficial layer over the whole surface of the 

 yolk. Mullns and Solea are the only genera whose ova undoubtedly have 

 the peripheral layer of yolk segments. It is pointed out that in Solea 

 and Mullus the central yolk is fused into one mass, while the peripheral 

 layer is segmented, and that this is an intermediate condition between 

 adhesive non-pelagic ova, where the yolk is made up of a number of minute 

 yolk spheres, and the continuous homogeneous single yolk sphere of pelagic 

 ova. From May 24th to July 17th a continuous supply of mackerel ova 

 were obtained, and Mr Cunningham thinks that the process of spawning 

 among such migratory fish as the mackerel is approximately simultaneous 

 in all specimens in a given locality. The specific gravity of mackerel ova 

 was ascertained to range between 1*0259 and 1*0265. There is a large 

 oil globule in the ovum, and it moves with perfect freedom at the surface 

 of the yolk, proving thereby that the yolk is a liquid with a very slight 

 tenacity. Tn floating ova the blastoderm is at the lowest pole and the 

 yolk at the uppermost. The yolk is described as a liquid enclosed by a 

 layer of protoplasm which is continuous with the blastoderm. After a 

 description of certain buoyant clupeoid ova, notes are given of ova, supposed 

 to be those of the plaice, whiting, pouting and rockling. A connection 

 between the presence of oil globules in the yolk and the normal quantity 

 of oil in the body of the parent fish leads the author to a hypothesis that 

 the excess of oil in the tissues of the parents extends into the ovum, and 

 during the development of the latter supplies the embryo with an abund- 

 ance of fat necessary to its growth. Mr Cunningham also gives the 

 results of his observations on the development of the vascular system and 

 coelom in the pelagic ova of teleostean fishes. 



In the same number there is also a paper on some ' Animal Colouring 

 Matters examined at the Plymouth Marine Biological Laboratory,' by 

 *Ne\v Ser., No. 1, p. 10, 1889. 



