V GROWTH IN TIME OF THE TOTAL ORGANISM 205 



have hitherto been developed" (Beverton and Holt, 1957). Newly investigated organisms 

 automatically fall into the categories (growth type) predicted by the theory even though 

 the latter is unknown to the investigator {e.g. Fig. 16, p. 197). Sometimes (crustaceans: 

 Roberts, 1957) a contradiction to theory was stated, but examination of the data seems to 

 indicate that the case in question actually falls into the growth type predicted. 



It is not to be expected, however, that the theory in its present state can do justice to 

 every phenomenon of growth observed. Specifically, the following facts have to be men- 

 tioned in criticism of the theory. 



/. The yeast Saccharomyces cerevisiae, being a spherical microorganism, was subsumed under 

 Type I. This corresponds to the observed growth curves (Fig. 5, p. 164) (Schmalhausen and 

 Bordzilowskaja, 1930; Bayne-Jones and Adolph, 1932; Bertalanffy, 1934). According to 

 the considerations indicated (p. 216), it was further to be inferred that cell size would 

 decrease with increase of temperature as is usually the case in unicellular organisms. 

 However, according to Christophersen and Precht (1954) energy metabolism (fermen- 

 tation) of the yeast, Torulopsis kefyr, is proportional to the dry weight of cells, thus referring 

 yeast into Type \\. The growth curves of the cells of the latter species were not investigated 

 but average cell volume increases with increasing temperature. Thus Bertalanffy's classi- 

 fication does not apply to this species which, however, is aberrant also in view of the fact 

 that it does not follow the usual rule of decrease in cell size with increasing temperature. 

 Christophersen and Precht emphasize that import of nutrient material (sugar) probably 

 is not to be considered a process of diffusion but rather as active transport due to enzymatic 

 reactions. Hence, Bertalanffy's supposition of a lower temperature coefficient for import 

 and assimilation would be invalid in this case. 



2. The results of different investigators on the dependence of metabolic rate on body size 

 show, in general, good agreement (p. i84f.) so that this relation appears to be a group- or 

 species-specific characteristic. There are, however, some exceptions. Fish (Table 10, p. 185 

 and Figs. 8-10, 12-14, p. i89ff.) have been subsumed under Type I, corresponding to many 

 experiments on metabolism and growth curves. However, in Salvelinus fontinalis a metabolic 

 exponent between 0.8 and 0.9 was found (Job, 1955), i.e. near to Type H. Plot of growth 

 data for this species (Carlander, 1953, p. 298f.) appears to show simple exponential 

 increase similar to Type H, different from the curve of length growth otherwise typical of 

 fish. This, if correct, would be a confirmation of theory. It is, however, an indication that 

 the classification summarized in Table 6 (p. 180) possibly is too generalized and that there 

 may be different metabolic and growth relations even within one taxonomic group. 



3. Zeuthen (1953, 1955) states that the curve of size-dependence of metabolism, inter- 

 specifically and intraspecifically, is composed of three segments. Interspecifically, the 

 constant a ?t 0.7 in unicellulars, a 5; 0.95 in small metazoa (ova, larvae, and animals 

 up to I mg N content), and a x 0.75 for larger poikilothermic and homeothermic 

 animals. Intraspecifically, Zeuthen contends a similar tripartite curve from the ovum to 

 the adult which would present a special case of the rule of ontogenetic recapitulation of 

 evolution. The physiological meaning of this broad comparison, ranging from bacteria to 

 mammals, is difficult to understand. Zeuthen disregards, however, the various types of 

 size-dependence of metabolism in postnatal development which are emphasized in 

 Bertalanffy's theory. He is certainly correct in emphasizing (1955) that "there are many 

 more 'metabolic types' which should be related to phenomena of growth than the three 

 suggested by Von Bertalanffy". On the other hand, the correlations between metabolic 

 and growth types, for which no alternative explanation is proposed, cannot be overlooked. 



4. It has to be asked to what extent the shape of growth curves, as assumed to be 

 typical in BertalanfTy's model, corresponds to the actual curves of growth. This 

 concerns {a) the initial, and {b) the late, phase of growth. 



(a) Backman (after Duspiva, 1955) objects that a point of inflexion is found 



Literature p. 253 



