EFFECTS ON THE HIGHER INVERTEBRATES 3 1 



Some specific changes in cell-structure are noted during various forms of 

 partial inanition. Thus calcium deficiency may loosen the intercellular attach- 

 ments, but it does not affect the ciliary mechanism, and apparently permits 

 mitosis to continue in the embryonic tissues of various invertebrates. Phos- 

 phorus and potassium, however, are evidently necessary for mitosis, as in plants. 

 In addition to the mineral salts, certain proteins, fats or carbohydrates, water, 

 etc. are doubtless essential to life, but we have as yet few data upon the morpho- 

 logical effects of their deficiencies among the higher invertebrates. 



Effects on the Developing Organism. — The effects of inanition upon the 

 developing invertebrate organism, especially during the earlier embryonal 

 stages, in many respects often differ markedly from those previously described 

 for the adult. The embryonal cells have a characteristic tendency to growth 

 and differentiation, which may enable certain organs and tissues not only to 

 persist but even to develop at the expense of the remainder of the starving organ- 

 ism. This is true for general inanition, and is also especially evident during 

 various forms of partial inanition; for example, in the case of specific salt defi- 

 ciencies in the sponges, coelenterates, etc. Thus in many cases it is evident 

 that deficiency in one limiting factor does not necessarily altogether inhibit the 

 development of the invertebrate organism when that factor is exhausted, but 

 occasions instead a disproportionate, abnormal growth, the extent and char- 

 acter of which will vary according to circumstances. Liebig's law does not 

 apply in these forms. 



On 'the other hand, in many cases the developing embryo or larva (in some 

 species even the adult organism) tends to undergo during inanition a series of 

 retrogressive stages more or less exactly reversing the normal order of develop- 

 ment. This process (technically called "reduction") is often well-marked in 

 sponges, coelenterates and planarians, though apparently rare in the more 

 highly organized invertebrates. Even in the lower invertebrates, however, there 

 is some question as to whether the (often remarkable) resemblance of the atrophic 

 organism to the earlier embryonic stages may not be more apparent than real. 

 But in some cases these atrophic remnants are actually able, under proper condi- 

 tions of nutrition, to regenerate the normal structure of the organism. Child 

 concludes that starvation results in morphological rejuvenation, followed by 

 physiological regeneration upon refeeding. 



The relatively great resistance to inanition usually offered by the gonads has 

 already been mentioned for adults. This applies also in some cases to the 

 developing organism, so that sexual maturity may occur in undersized bodies 

 as a result of underfeeding (e.g., silkworm and certain bees). But in others 

 (starfish) sexual maturity is reached only upon the attainment of a certain body 

 size, or the development of the gonads may even be entirely inhibited by inani- 

 tion (fruitfly). 



The sex of the offspring (as already mentioned) may also be influenced through 

 the effect of inanition upon the germ cells in the larval stages, particularly at 

 certain critical periods (rotifers, daphnids, aphids, etc.). In some insects, sexual 

 maturity appears to be determined entirely by larval nutrition, in others chiefly 



