SECTIONAL TRANSACTIONS.— D. 561 



9 males and 1 female, 3 males, and 1 male. For reasons to be given the appearance 

 of these ' occasional * females is not regarded as controverting the idea that the 

 mothers were really male-producers (arrhenotokous). The species is therefore 

 predominantly thelytokous. 8o far four successive parthenogenetic generations have 

 been obtained, but the significance of male-production remains undetermined. 



In saw-flies the parthenogenetic production of both sexes by the same female, 

 where undue preponderance of one or other sex does not obtain, is known in two 

 species only. The case discussed here is different, and is a new record, for the two 

 sexes are produced by two kinds of females, one kind male-producing and the other 

 female-producing. The biological significance of this will be discussed. 



Dr. G. S. Carter. — The Structure of the Ciliated Cells of the Velum in the 

 Veliger of Aeolidia papillosa. 



The nerve-supply and the cytoplasmic structure of these cells has been investigated 

 as far as possible in fresh material by the use of vital stains. Intracellular nerve-fibrils 

 were found, ending near the basal granules and connected with the nerve-supply 

 described in a previous paper. The ciUum is complex and consists of numerous 

 simpler units. Each of these consists of an external fibre, a basal granule and two 

 similar structures in the cytoplasm of the cell, and of a columnar element of protoplasm 

 passing inwards from the base of the external fibre. One of these units, and not the 

 whole cilium, is the true unit of ciliary activity in these cells. 



The chemical nature of these structures as displayed by histo-chemical reactions 

 was investigated. The basal granules contain lipoids and probably also carbo- 

 hydrates. Lipoid vacuoles of two types are present in the cytoplasm of the cell. 

 Those of one type are large and lie near the base of the cell, and appear to contain 

 the reserve food-materials of the cell. Those of the second type lie near the ciliary 

 apparatus, contain fatty acid, and can be seen to circulate around the part of the cell 

 in which they lie. They appear to play some part in the activities leading to the beat 

 of the cUium. 



The bearing of these observations on recent theories of the chemical mechanism 

 of ciliary activity is discussed. 



Mr. A. D. HoBSON. — Some Aspects of the Relation of Salts to the Unfertilised 



Egg- 



Artificial parthenogenesis of the eggs of certain invertebrates can be induced by 

 treatment with isotonic solutions of calcium chloride when the hydrogen ion concentra- 

 tion is approximately the same as that of sea-water. Potassium chloride is, under the 

 same conditions, relatively ineffective in causing parthenogenesis owing to inhibition 

 of the process of maturation. Mixtures of potassium and calcium chlorides may be 

 very efiective parthenogenetic agents. The discrepancy between these results and 

 those of R. S. Lillie, and the relation of the process of maturation to the initiation 

 of development is discussed. 



Miss D. Strangeways. — A Comparative Study of Leucocytes and Fibro- 

 blasts cultivated in vitro. 



The question of the origin of fibroblasts is of importance in connection with the 

 study of tissue repair. Many workers hold that under certain conditions the non- 

 granular leucocytes of the blood and lymph may become transformed into typical 

 fibroblasts, and state that this transformation is readily observed when the leucocytes 

 are cultivated in vitro. As a result of the investigations recorded in this communica- 

 tion, however, it would seem that much of the evidence cited in support of the above 

 view is open to serious criticism. In vitro cultures of leucocytes from the peritoneal 

 exudate and of normal fibroblasts have been studied in the living condition by means 

 of dark-ground illumination, and the effects of various fixatives upon the appearance 

 of the two types of cell have also been investigated. As a result of these observations 

 it has been found that transformed leucocytes differ from the fibroblasts (a) in their 

 smaller nucleo-plasmic ratio, (6) in certain important cytological features, and (c) in 

 the character of their intra-cellular and amoeboid movements. 



1928 O O 



