A TYPICAL ORGANELLE — CHEMICAL NATURE 29 



Watson et al. showed that both the membrane and the full 

 complement of fibrils were present in their preparation of isolated 

 cilia. Tibbs seem.s satisfied that the membrane and matrix contri- 

 bute little to the dry mass of the organelles. 



All authors found that most of the material of the cilium was 

 protein, although lipids, which probably came from the sheaths, 

 form an appreciable part of fish sperm tails. This second observa- 

 tion confirms the findings of Miescher (1897) on salmon sperm and 

 Zittle and O'Dell (1941) on bull sperm. The protein material 

 appears to be largely in the " alpha " form, and hydroxyproline is 

 absent, so that the protein could not be collagenous (Tibbs). In 

 addition to the protein material, both cilia and flagella, though not 

 sperm tails, contained a small proportion of nucleotide material, 

 mainly as ribonucleoprotein, but, while Child found about 2*5 per 

 cent of RNA, Watson et al. only found about 0-3 per cent in the 

 same material. Enzymatic activity in the form of an apyrase 

 capable of splitting phosphate from adenosine phosphates was 

 found by Child and Tibbs, although Child found that the cilia 

 preparation was most active on adenosine-5 -monophosphate, while 

 Tibbs' flagellar extract was more active on adenosine triphosphate 

 and adenosine diphosphate and much less active on adenosine 

 monophosphate and beta-glycerophosphate (see also p. 108). A 

 small amount of carbohydrate material was present in both cilia 

 and flagella. 



Earlier workers had found that the ciliary or flagellar fibrils were 

 digested by proteolytic enzymes, e.g. Pitelka and Schooley (1955) 

 found that the axoneme (fibre bundle) of Euglena was disrupted by 

 trypsin. Grigg and Hodge (1949) even found a difference between 

 the central and peripheral fibrils, for the two central fibrils of the 

 cock sperm were more easily destroyed by pepsin than the 

 peripheral fibrils. The central fibrils of sperm of Psammechinus 

 are also more easily disrupted than the peripherals (Bradfield, 

 1955) and so may be of a different constitution. 



The very large comb -plates of ctcnophores, with cilia up to 

 2 mm long in clumps of 100,000 or more cilia should offer ideal 

 material for some biochemical and biophysical studies. 



Bacterial fiagella, which are also proteinaceous and have been 

 studied by several groups of workers (e.g. Astbury and WeibuU, 

 1949; De Robertis and Franchi, 1951), are probably not identical 



