70 H. V. NEAL 
words, are not ‘paths’ utilized by the neuraxones as a means of | 
conduction and material for growth, as assumed by Held (’09), 
but are ab initio nervous. The participation of indifferent 
(neurilemma or glia) cells in the formation of the motor nerve 
anlagen in elasmobranchs by means of the migration of medullary 
cells along the nerve anlagen (‘plasmodesmata’) has been de- 
scribed by many, including the writer (’03—’14), but it is not such 
cells which form the primary plasmodesmata. Admitting the 
possibility that in the plasmodesmatous connection shown in 
figures 3 to 5 of this paper processes of indifferent, non-neuro- 
blastic cells occur, nevertheless the important fact remains that 
the primary neuromuscular connections were not formed by 
these indifferent, non-nervous elements. Their relations to the 
nerve anlagen are secondary and not primary. 
In the light of the evidence that neuromuscular connections 
are ab initio nervous, there seems to be little justification for the 
application of the term ‘plasmodesmata’ to them. What we 
are actually dealing with in the case of such structures are nerve 
anlagen, or neuraxones and their sheaths. Why then term them 
plasmodesmata, thereby suggesting that they are merely non- 
nervous, undifferentiated intercellular connections? 
SUMMARY 
1. Previous to the stage of 4.5 mm. there are no protoplasmic 
connections between tube and myotomes in Squalus embryos. 
2. Neurofibrillar substance is present in the primary connection 
between tube and myotome. Within the plasmodesmata of 
Paton (’07) and Held (’09) may be found in adequately stained 
Bielschowsky-Paton preparations deeply stained neurofibrils 
which may be traced to bipolar neuroblasts within the neural 
tube. The assertion that the primary connection between 
muscle and nerve is non-nervous, i.e., non-neurofibrillar, is based 
upon incompletely stained preparations. 
3. In stages before protoplasmic connection between tube and 
myotome is effected certain medullary cells in zones where later 
the nerve anlagen (‘plasodesmata’) make their appearance 
show in successfully stained Bielschowsky-Paton preparations 
