662 R. C. PUNNETT. 
apparently devoid both of structure and of nucleus. The origin of these bodies, the “ fettartig 
Kiigelchen” of Spengel and the “eosinophil globules” of Willey, is somewhat obscure. Willey 
holds that they are the products of nuclear degeneration accompanied by hypertrophy of the 
nucleolus. Spengel (?O8, p. 306) refuses to believe that they are the outcome of degenera- 
tive changes. In the young specimen of Pt. laccadivensis referred to above I have been 
able to follow what seems to be the history of these bodies. Certain of the spindle-shaped 
mesodermal cells become first oval and then more or less spherical in shape (PI. XL. 
fig. 38, a—b), at the same time increasing slightly in bulk. A few granules make their 
appearance in the hitherto clear cytoplasm. A little later these cells appear to collect 
together in clusters of about 6—10 (fig. 38, c), which subsequently fuse together to form 
giant cells packed with granules and with the nuclei degenerating (fig. 38, d and e). Later 
the nuclei disappear and the giant cells apply themselves close to the gonad. Where this 
occurs the wall of the gonad seems to break down and by some method which is not clear 
the nutriment stored in the giant cells is transferred to the interior of the gonad where 
it loses its granular appearance (cf. Pl. XL. fig. 37). At later stages small round corpuscles 
of an eosinophil nature also make their appearance in the mesoderm and subsequently apply 
themselves to the gonads in a similar manner (Pl. XL. fig. 41). The chief interest of the 
process seems to lie in the fact that although the sexual cells themselves are derived from 
the ectoderm’, it is the mesoderm which provides them with nourishment and which con- 
tributes the yolk to the eggs. 
The above account is of interest when it is considered with reference to our conception 
of the nature and properties of the coelom. According to present ideas one of the chief 
functions of the coelom is to give rise to the generative cells from the epithelium which 
lines it. Further it is usually held that the most primitive method of formation of the 
coelom is that of archenteric diverticula. In animals like the Enteropneusta, where this 
method of the formation is found, we should naturally look for genital cells arising from 
its lining. That this is not so may cause us to regard with some reservation the statement 
that the coelom was originally a gonocoel’, and to consider it rather as an organ specialized, 
among other things, for the reception and maturation of the genital cells. 
VARIATION IN PTYCHODERA FLAVA. 
The different varieties of Pt. flava are by no means easy to distinguish from one another 
after preservation. An adequate examination of the characters which are of systematic value 
involves the preparation of a large number of serial sections. If a trustworthy criterion based 
upon external features alone could be found much labour might be spared the Enteropneustic 
systematist. The large amount of material collected by Mr Stanley Gardiner has enabled 
me to attempt this. 
The characters upon which such a criterion might be based must satisfy two conditions; 
(1) they must be capable of easy measurement, and (2) they must be independent of the 
1 In this connection it is interesting to notice thatsolong figs. 88 and 89). 
ago as 1885 Hubrecht described the ectodermal origin of the 2 For the most recent general account of the coelom the 
gonads in the Nemertean Lineus gesserensis. He was able reader may be referred to Lankester’s Treatise on Zoology, 
here to distinguish with certainty the primary ectodermal 1900, Pt. 1. chap. 11. 
connection from the later formed duct (Hubrecht, ’85, PI. vy. 
