Occasional Papers of the Museum of Zoology 5 



solution of toluidin blue or thionin with or without a contrast 

 stain of erythrosin it may be readily determined that there is 

 no union of these ducts, but that they lie parallel to each other 

 and very close together. The toluidin blue or the thionin stains 

 only the contents of the glands and their ducts while the mem- 

 brane remains unstained. Between the deeply stained masses 

 of contents of the ducts may be perceived the thin line marking 

 the membranes of the ducts. The other stains used color the 

 membranes as well as the contents of the ducts, hence the two 

 ducts appear as one. It seems that Xicoll (1912) in describ- 

 ing the cephalic glands of Ccrcaria ordinata may have erred 

 in considering that the ducts of each pair have united to form 

 a single duct. 



The nature of the secretion produced by the cephalic glands 

 has not, as far as the writer is aware, been determined. Cort 

 (191 5) called these glands cephalic or stylet glands. How- 

 ever, since they are present in cercaria in w^hich a stylet is not 

 present it seems doubtful that the cephalic glands have anything 

 to do with the formation of the stylet. It is here suggested 

 that these glands produce mucus. In support of this view may 

 be presented the evidence that their secretion is in the condi- 

 tion of fine globules which stain blue or purplish blue wdth 

 toluidin blue or thionin. These are specific mucin dyes yield- 

 ing a metachromatic stain. Haemotoxylin also stains mucin 

 deeply but it cannot be depended upon as a test for mucin. - 



^ Tha writer is here constrained to make an appeal for the use of better and 

 more varied staining methods in the study of parasitic worms. Haematoxylin and 

 carmine dyes because of the ease with which they may be used are employed to 

 the almost total exclusion of other dyes. It is admitted that eosin and erythrosin 

 are used with haematoxylin as contrast stains. These stains, however, reveal but 

 little. The result of the employment of this limited technique is that the products 

 of many glands, their function, and the finer histological structure of numerous 

 parasitic worms is little understood or the wrong ideas have come to prevail. The 

 well trained pathologist, histologist, or bacteriologist makes use of a large number 

 of stains and micro-chemical tests in securing his data. The time is ripe for the 

 helminthologist, as well, to employ a varied technique. 



