DEVELOPMENT OF BALANOGLOSSUS KOWALEVSKII. 9] 
due to thickening of the ectoderm and the appearance of 
numerous mucous glands on the skin. The whole skin is 
uniformly ciliated from the time when the blastopore closes 
throughout life. 
At about seven to eight gill-slits the suctorial tail disappears, 
probably atrophying rapidly, but as to this process nothing more 
can be predicated. It is to be found in some larve with eight 
gill-slits, while others in the same stage are without it. The 
anus is then terminal, circular, and permanently open. 
At ten gill-slits the ovaries are first perceptible, but as yet 
are not marked enough to appear in a surface view. In older 
animals they form large yellowish-grey projections from the 
sides of the body. Their minute structure, together with that 
of the testis, will be given later. 
The body of the adult is very highly coloured, the proboscis 
being of a yellowish-white tint. The collar is a brilliant red 
orange (especially in males), with a white line round the edge 
of the operculum, while the rest of the body is of an orange 
yellow, shading to pale green yellow in the intestinal region, 
which is semi-transparent throughout life. The distinction 
between the colour of the males and females is very well 
marked in B. Kowalevskii, the genital regions being grey in 
females and yellow in males. The sexes are of different colour 
in all the Enteropneusta, most prominently so in B. sal- 
moneus (Giard), in which the males are chrome yellow and 
the females salmon coloured. 
It may be well, before passing to the internal development, 
to mention the peculiar odour which the creatures possess. 
This odour is very penetrating and persistent, resembling that 
of chloride of lime with a fecal admixture. All the species of 
Enteropneusta which I have examined alive possess more or 
less offensive odours. This peculiar property is most developed 
in B. Brooksii (new species), in which the smell is very 
distinct after the animals have been months in spirit, which 
has been often changed. The smell of this species is strongly 
suggestive of iodoform. It is so powerful as to be a con- 
siderable drawback to investigating the species. 
