57 

 the form on the Californian coast and is Hyalodiscus laevis. But they 

 are ali the same and constitute one form. Kùtzing is the only per- 

 soli who has studied them from the living forms except Montagne. 

 But these various forms enumerated are ali one form varying sli- 

 ghtly as different authors see them. 1 have seen the Bacillaria living 

 and gathered them in profusion. I have seen Hyalodiscus cervìnus T. 

 B. where it changes into Hyalodiscus subtilis J. W. B. and that into 

 Hyalodiscus Whìtneyii, Californicus , Franklinii, laevis and Patago- 

 nicus. 



It can be seen also in the Matacuta specimen that Hyalodiscus 

 subtilis evoluted or changed from Melosira Borreri R. K. G. Which 

 I had some years ago shown is a form of Melosira nummuloides, a 

 marine form which grows in orofusion (it grows almost everywhere 

 in brackish water) of Melosira varians C. A. Ag. This is a fresh water 

 form and extremely common being found in almost every spring 

 the world over. In turn it seems to be evolvel from a Conferva. 

 When Trochiscia monilìformis first appears it is a single pili box like 

 individuai. Or a single sphere. Soon it grows by adding individuals 

 one to the other and a chain is formed. This is growth. Now the 

 anthozoa - like organs impregnate the ova - like organs and dissappear 

 and it is about to increase by means of the formation of seeds or 

 spores. But these individuai are larger than the ordina ry forms. As 

 they seem to increase in size at the time and the they become 

 forms that are known as Hyalodiscus. This was shown some years 

 ago is the same form as Melosira nummuloides L. W. D. which is 

 a brackish and marine form. It is evolved and grows from Melosira 

 varians C. A. Ag. The enlarged individuals are like Melosira nummu- 

 loides only several times the size and separate from the chain and 

 move off. It is rare to find them in contact with the chain but I 

 have drawn it just asw it was separating. And instead of fixing 

 itself like the Melosira by the fiat side of the valve it attaches itself 

 to submerged algae, and even other Bacillaria by the edge of the 

 valve and this foot is sometimes quite long and forms a « pedicell » 

 as it is called. Showing that the whole Bacillarian has protoplasm 

 also and is not the Diatom in hardened shell alone. I have seen 

 this common ali along the Pacific coast of California, Oregon and Wa- 

 shington. And now it appears in Alaska. I got it thirty five years ago 



