500 JOSEPH STAFFORD, 



the cuticle to close over the mouth again or for an additional layer 

 of cuticular substance to be formed. At any rate during the growth 

 of the animal there are continually new glands being formed and 

 these must first fill with secretion and exert sufficient pressure to 

 break through the already formed cuticle. In all these cases one 

 can readily see that a drop may be held between the outer denser 

 layer of cuticle and the skin musculature through which the duct 

 must pass. 



As to the distribution of these glands Aspidogaster forms no 

 exception to the generally occurring conditions. In the mouth trumpet 

 and neck they are most numerous, where the great majority of their 

 outwardly conducting tubes rum forwards and open on, or in proximity 

 to, the rim uf the mouth. Numbers, however, open on the surface, 

 generally on the ventral and lateral walls of the neck as far back as 

 to the genital opening. In exceptional cases I have seen them uni- 

 formly distributed all along the sides and back of the animal right 

 back to the posterior end. 



Zacharias describes "einzellige Schleimdrüsen" and im- 

 mediately afterwards speaks of one of them as two "zusammen- 

 hängende Zellen" in one of which he figures a nucleus. At the 

 beginning too he says: "mit Sicherheit unterschied ich zahlreiche, 

 blass-blau gefärbte Drüsenzellen", but at the end of his description of 

 these particular glands he speaks of them as "hypothetische 

 Drüsenorgane". He did not follow them to their external openings. 

 Another kind of glands composed of "zusammenhängenden und 

 unter einander anastomosirenden Zellen" with nucleus and duct which 

 he traced to the cuticle he also describes. This network of "ein- 

 zelligen Drüsen" he found distributed over the "gesammte Körper- 

 o])erfläche" but most numerous in the neck. It is not my intention 

 to explain how the numerous errors of observation found in the 

 literature of Aspidogaster have arisen. That could hardly be counted 

 of scientific importance. Patience and repeated search in numerous 

 preparations is the best guard against mistakes. I have, also, often 

 seen cases where two glands seemed to join, or where a gland ap- 

 peared to branch; when, upon inducing a change of position, it would 

 be seen that where a duct was apparently wanting it would be found 

 covered by another gland, or by other means rendered invisible. 



An especial grouj) — circum-pharyngeal glands (Fig. 1, 

 7 P6r) — lies round the pharynx on all sides and either closely 

 applied to its walls or many of their blind, expanded, free ends 



