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DR J. H. ASHWORTH AND PR JAMES RITCHIE ON THE 



The second type of variation consists in the development of two tentacles. In 

 another male sporosac (text-fig. 3, B) one of the tentacles is of normal length, while 

 the other is little more than a bud. The remainder of the sporosac is normal, so 

 that the abnormality may be regarded as a sport tending towards the condition 

 represented in the two-tentacled sporosac of Dicoryne conferta. 



In the solitary abnormal female sporosac two well-developed tentacles, each of 

 normal length, are present (text-fig. 3, C). These arise contiguously, and resemble in 



a b c 



Text-fig. 3. — Three abnormal sporosacs of Dicoryne conybearci, from Naples, x 250. 



their arrangement and divergence the tentacles of the sporosac of D. conferta. In 

 our specimen, however, the spadix appears to be double, a branch embracing either 

 side of the single oocyte. The simplest interpretation of this condition is probably 

 that here the phenomenon of duplication of parts, moderately common in other 

 groups of animals, is exhibited. 



Early Developmental Stages of Dicoryne conybearei. 

 (PL VIII, figs. 11, 12, 13.) 



A considerable number of free-swimming sporosacs of D. conybearei of both 

 sexes — but males predominating — were kept alive in small vessels for a day or two, 

 and many of them shed their genital products. About sixteen of the eggs had been 

 fertilised and had passed through the cleavage phases before the material was 

 preserved. 



The earliest stage of development represented is a blastula (fig. 11), slightly oval 

 in form, about 100 fi long and 90 /x broad, and consisting of about 120 similar cells 

 which surround the large central cleavage-cavity or blastoccele. Cleavage of the egg- 

 was total, and apparently equal or nearly so. Cell-outlines are present though not 

 easily seen, as the cells are loaded with yolk-spherules of different sizes. In each 

 blastomere is a peripheral zone of minute granules of uniform size, which differ from 

 the yolk-spherules in their reactions to stains. These granules — the presence of 

 which in the oocyte has been already noted (p. 2G4) — remain peripheral throughout 

 development and are found, though in diminished number, in the ectoderm cells of 



