“a 
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they presented; and with this, as well as other objects, in view, 
Raja embryos have been reared and preserved during the past three 
years. 
The demands in time and energy of this research have been 
greater then could have been imagined or desired, but the resulting 
facts seem to be so novel that the labour has perhaps not been in vain. 
Attempts to obtain an even moderately good series of Scyllium 
embryos failed, and, as I have not seen anything like all the facts 
‘about to be described in Elasmobranchii other than Raja, I feel by 
no means certain that identical conditions obtain elsewhere'). The 
stages of Scylliidae in my possession are none of them critical ones; 
that is, they do not reveal the apparatus in its highest development, 
or as I met with it in Raja at certain periods of the ontogeny. 
The wealth of the ganglion cells in a particular region of Raja (to 
be presently defined) exceeds so much anything that I have as yet 
met with in other forms, that in many at least of these latter I feel 
inclined to conclude a more rudimentary character of the apparatus. 
Time has not been at my service for the closer investigation of many 
types, and, even now, it is not probable that every detail in the 
history of the apparatus in Raja has been made out. 
My series of embryos of this form is what many might judge 
to be complete, numbering, as it does, some 300 specimens of all 
ages and sizes. None the less there are gaps in the collection, and 
these are often of a sort that it may not be easy to fill in. No two 
embryos are exactly alike in all the pictures which they yield of this 
apparatus, and in half a dozen specimens, which would be taken to 
be of the same age (from their sizes, from a comparison with BALFOUR’S 
stages, or from the more certain criteria of number of gill-clefts, 
protovertebrae etc. etc.), it is quite common to find this transient nervous 
system, like other organs”), in widely different stages of development, 
and presenting great variations in detailed characters. 
1) Very similar things were found in Lepidosteus also, and 
there, too a motor function could be made out for the apparatus. The 
sections of Lepidosteus are far more difficult of interpretation than 
those of Raja, but the main facts appear to be the same as in the latter 
genus. 
2) In my researches on Raja I have been compelled to give up 
completely any attempt to make use of Batrours nomenclature. With a 
limited number of embryos at one’s disposal it is no doubt easy to fit 
them into one or other of the well-known stages; with an increased 
number this become more difficult or even impossible, so great are the 
variations met with. 
