72 REMARKS UPON APPENDICULARIA AND DOLIOLUM 



red colour, caused by presence of multitudes of spermatozoa, whose 

 development from the circular cells may be readily traced. 



This orange-red mass, or rather masses, for there are two in juxta- 

 position, is described by Mertens as the " Samen-behalter " or vesiculse 

 seminales. He describes them as making their exit, bodily, from the 

 animal, and then becoming diffused in the surrounding water. This 

 circumstance, indeed, appears to have furnished his principal reason 

 for believing these bodies to be what the name indicates. 



The spermatozoa have elongated and pointed heads about 5-D"Virth 

 of an inch in length, and excessively long and delicate filiform tails. 



Mertens describes as an ovary, two granulous masses, which he says 

 lie close to the vesicul^ seminales, and have two ducts, which unite 

 and open into this " ovisac.'' 



This appears to me to be nothing more than the granulous greenish 

 mass of cells and undeveloped spermatozoa, which exists in the testis 

 at the same time as the orange-red mass of fully developed spermatozoa. 

 I saw nothing of any ducts, nor do I know what the " ovisac " can 

 be, unless it be a further development of an organ which I found in 

 two specimens (fig. 3 g), consisting of two oval finely granulous 

 masses, about -a-o-oth of an inch in diameter, attached, one on each 

 side of the middle line, to the dorsal parietes of the respiratory 

 cavity, and projecting freely into it. 



Mertens' " ovisac " has about the same position as these bodies, 

 and he says he saw " living animals " proceed from it, the part being 

 afterwards evidently collapsed. 



Unfortunately, however, he does not appear to have noticed the 

 endostyle, whence confusion might readily arise ; nor does he give the 

 slightest hint as to the nature of the " living animals " which he saw 

 come forth. 



85. Still less am I able to give any explanation of the extraordinary 

 envelope or " House " to which, according to Mertens, each Appendicu- 

 laria is attached in its normal condition. I have seen many hundred 

 specimens of this animal, and have never observed any trace of 

 this structure ; and I have had them in vessels for some hours, but 

 this organ has never been developed, although Mertens assures us 

 that it is frequently re-formed, after being lost, in half an hour. 



At the same time it is quite impossible to imagine, that an account 

 so elaborate and detailed, can be otherwise than fundamentally true, 

 and therefore, as Mertens' paper is not very accessible, I will add his 

 account of the matter, trusting that further researches may clear up 

 the point. 



The formation of the envelope or " Haus " commences by the 



