456 SUMMAEY OF CUREEXT RESEARCHES RELATING TO 



gradual sinking in the water, and a coming to rest in depths of from 

 5-30 fathoms, but for the most part in 10-25 fathoms. 



Next spring a denatant inshore migration occurs and a concentration 

 of the products of the previous year's spawning season. There is a 

 contranatant migration into deeper water again at the end of summer. 

 Thereafter there is a seasonal migration from deep water to shallow 

 water, the spring migration being from the north and the autumn 

 migration to the north (east coast of Britain, north of the Wash). 

 With increase in size the outward migration is still further to the north 

 and into deeper water. Coming maturity impels the fish to migrate in 

 winter contranatantly to a still greater distance, from which it will 

 return with the spawning migrants. The outward migration may 

 associate the fish with spawners of a region related to another school. 

 After spawning the spent fish join the summer denatant migrants and 

 migrate later than these, and evidently further than these for winter. 



Spawning in Algerian Sp^ridse.* — J. B. Bounhiol and L. Pron 

 find that there are two annual periods of reproductive activity in some 

 Sparidfe. In Pagellus erythrinus there is spawning between 1st March 

 and 1st August, at a temperature of at least 16° C. at depths of 20-30 

 metres. It is preceded by gradual ovarian development lasting for two 

 months ; it is followed by retrogressive changes. In the last two weeks 

 of October and the first week of November there is rapid ovarian 

 development ; then spawning occurs ; then retrogression sets in, 

 completing itself about the middle of December. The temperatures at 

 the time of the second reproductive period are from 21° to 15 C. at a 

 depth of 30 metres. Various facts relating to reproductive precocity 

 and sex dimorphism in Sparidae are chronicled. 



Development of Erythrocytes from Hsemoglobin - tree Cells, f — 

 P. G. Shipley explanted some tissue from the area opaca of chick 

 embryos before the formation of blood islands and the elaboration of 

 htemoglobin. The cultures were planted in the blood-plasma of an 

 adult hen after Harrison's method, and in some of them hemoglobin- 

 bearing cells developed from amoeboid colourless elements apparently of 

 mesoblastic origin. In all the cultures (120) there was vigorous cell 

 proliferation and migration which began within an hour after the 

 culture slides were placed in the incubator and continued for three to 

 four davs. This growth was so exuberant, and cell migration was so 

 rapid, that in twenty-four hours the layer of new cells was perceptible 

 without the aid of a lens, and in forty-eight hours a ring of new tissue 

 3 or 4 mm. in diameter was formed about the original explant. The 

 study of the cultures showed that development and differentiation 

 of haemoglobin-bearing cells is possible in tissue transplants removed 

 from the normal environment to a culture medium. The development 

 of erythrocytes (mostly abnormal, however, in size and shape) from 

 amoeboid colourless ancestors and the specialization and assumption of 



* C.R. Soc. Biol. Paris, Ixxix. (1916) pp. 140-3. 

 t Anat. Record, s. (1916) pp. 347-53 (2 figs.). 



