NOTES on a TRACT of MODIFIED ECTODERM 
in Crania anomala and Lingula anatina. 
By Auice Hearn. 
With Plates ITT., IV. and V. 
[Read 10th December, 1887.] 
THE interest attaching to the Brachiopoda is so great, 
and touches the naturalist at so many points, as to be an 
ever present excuse for studying them with care and in 
such detail as is possible. The mere fact of their enor- 
mous distribution in time is of itself very fascinating ; 
whatever modifications may have taken place in the softer 
tissues the skeletal portions have been most persistent in 
many forms which have survived to the present time, 
while the close resemblance of many living forms to one 
another points to but comparatively slight individual 
variation since the early Brachiopoda separated from 
the main invertebrate phylum. The homologies of the 
different organs with those of other invertebrate forms is 
of great interest, and has received attention from various 
investigators. In one way and another Brachiopods claim 
attention on various grounds, and, to judge by the mass 
of literature on the subject, they have been very fairly 
worked at. 
With regard to Crania, in particular, comparatively 
little detailed work seems to have been done until quite 
lately ; in 1886 the results of some very careful observa- 
tions made by M. Joubin, at the marine laboratory of 
Banyuls-sur-Mer, appeared in the ‘“‘ Archives de Zoologie 
Expérimentale.”* This paper is prefaced by a detailed 
* Ser, 2°, tome iv., p. 161. 
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