RECENT ADVANCES OF ZOOLOGY. 287 
developed, and makes its way to the exterior through their 
openings. 
This view of the importance of a combination of characters 
has widely extended itself among zoologists, and has led to 
valuable results in other divisions of the Animal Kingdom than 
that of Vertebrata; but of these I shall hardly have time to 
speak to you to-day. 
Startling as is the doctrine that the Vertebrates and some of 
Prof. Huxley’s Molluscoids are intimate allies, I must now ask 
you to consider the possibility of your zoological affinities with 
‘members of the still lower group of what are ordinarily called 
Worms. 
I will do my best to save your feelings of self-respect by 
introducing you first of all to a distant cousin, who has at least 
this regard for his more distinguished relatives, that he has quite 
cut himself off from all the rest of the mob which zoologists call 
‘Vermes’ or Worms. More than this, he has a very high-sounding 
name indeed—it is Balanoglossus; and he has a thoroughly 
respectable name-father in the distinguished Italian naturalist 
Delle Chiaje. 
It has long been known that this worm, which lives in sandy 
or muddy places, takes in water by its protusible proboscis, and 
passes it out through slits, which lie on either side of the anterior 
part of the body; and that these breathing-slits or gill-slits are, 
in all their essential morphological characters, justly comparable 
to the gill-slits of Fishes. This is a fact which is so thoroughly 
recognised that some time ago we had a diagram prepared for 
exhibition in the galleries of the new Natural History Museum at 
South Kensington. Curiously enough, on the very day on which 
_I put into position that picture, and its appended label of 
“A Worm that breathes by gills, like a Fish,” Mr. William 
Bateson, of St. John’s College, Cambridge, read a paper before 
the Royal Society which gave a new aspect to the relationships 
of Balanoglossus. 
Mr. Bateson has had exceptionally good opportunities for 
studying the history of this form,—we had better at once cease 
to call it worm,—owing to the excellent arrangements for marine 
laboratories which now obtain in the United States, and the 
hospitalities of their distinguished directors. 
Mr. Bateson has been able to observe the development of 
