vi CHROMIDIA 195 



firmation. Indeed, even the occurrence of chromidial extrusion is not 

 undisputed. Thus Duesberg (1911 a) denies the nuclear origin of the 

 " chromidia" described by Wassilieff in Blatta (Fig. 81, E) and holds them 

 to be chondriosomes (see below), and therefore of purely cytoplasmic 

 origin. Meves also denies the derivation from the nucleus of certain 

 bodies, which have been described by the upholders of the chromidia 

 theory as having been so derived. Beckwith (1914) has subjected the 

 egg of Hydractinia to a very careful examination, and comes to the 

 conclusion that the staining particles there present, which must un- 

 doubtedly be of the same nature as the similar bodies described by 

 Schaxel in so many oocytes (including those of several Hydrozoa), are 

 of cytoplasmic, and not of nuclear, origin. She bases this conclusion 

 on the fact that they make their first appearance scattered through the 

 cytoplasm and not concentrated round the nucleus, and also on the 

 fact that though they react similarly to chromatin to many stains, 

 they show striking differences in their reaction to others. The doubts 

 thus thrown on the nuclear origin of the " chromidia " in the Metazoa lead 

 us on to a consideration of the chondriosomes, which, as we shall see, 

 may or may not be identical with chromidia. 



(2) Chondriosomes 1 



These are granular or filamentar bodies present in the cytoplasm, 

 about the nature of which there has been much controversy during the 

 last few years. Some cytologists have ascribed to them a role in 

 morphogenesis and heredity equal to that of the chromosomes. This 

 theory has been especially developed by Meves (1908, 1911, etc.) and 

 Duesberg (1911 6, etc.), following on the work of Benda. An exhaustive 

 review of the literature on the subject up to the year 1911 is given by 

 Duesberg (1911 b). 



An account of the chondriosomes in the spermatogenesis of Blatta has 

 already been given (Chapter III.). They may take the form of granules, 

 chains or filaments. They stain strongly with many stains, including 

 the commoner chromatin stains, though towards others they react 

 differently from chromatin, which fact is an important argument against 

 their being the same as chromidia. By certain fixatives, especially 



1 This subject has suffered, like most other branches of science, from changes of nomen- 

 clature accompanying extension of knowledge or change of view. The following summary 

 will be of use to the student who wishes to follow up this subject in the original literature : 



General term =Chondriosome (Meves) = Plastosome (Meves). 



Chondriosomes in form of granules = Mitochondria (Benda) Plastochondria (Meves). 



Chondriosomes in form of rods or filaments =: Chondrioconts (Meves) = Plastoconts (Meves). 

 Chondriosomes in form of chains of granules Chondriomites (Benda) . 



The change in the prefix in Meves' latest set of terms signifies his view of their histo- 

 genetic function (1911). Paraplastic bodies (Meves) are bodies developing from Plastosomes. 



