462 Annals New York Academy of Sciences 



may take place in a limited number of ways of which the following are known: 

 (a) tetrahedral — resulting in trilete spores; (b) abortive — same as (a) except 

 that only one spore develops fully; and (c) rhomboidal — resulting in monolet 

 spores. 



The most common form, tetrahedral meiotic division, necessarily results in 

 trilate spores with three-sided symmetry. Some of the organized elements 

 from carbonaceous chondrites described by G. Claus and B. Nagy appear to 

 resemble such trilete spores. It should be emphasized that in CirciiUna sp. 

 of the upper Trias — although similar to the above-mentioned organized ele- 

 ments — the tetradic (trilete) mark is not evident. 



The existence of truly multicellular organisms is allied to the function of 

 reduction division; otherwise, polyploidy would result. We know, however, 

 that in terrestrial conditions tetraploidy may cause sterility. 



A so-called Dauerstadimn is usually linked with the formation of spores or 

 sporomorpha. Protecting the plasma is a strong hull which consists of the 

 exine or the sporoderm and the intine. The sporoderm is made up of sporopol- 

 linin, a terpene derivative, which can become soluble in the presence of oxygen 

 but is very resistant and capable of fossilization in the absence of oxygen when 

 minerals are present. It can bind iodine, bromine, and chlorine. During coal 

 and peat formation, where bacterial activity is reduced because of the acidic 

 environment, spore preservation is enhanced. Under suitable conditions rich 

 deposits of sporoderms may occur (fimminit). 



The Dauerstadmm allows the organisms to live through highly unfavorable 

 periods — an especially important consideration if they are subjected to wide 

 variations in environment, such as extremes of cold or drought. 



The majority of skeleton-forming fossil protobionta lived in the oceans of 

 primeval tmies, although sporomorpha and spores form in marine, limnetic, 

 and terrestrial biotopes. Adequate preservation of all residues of organisms 

 depends upon the particular fossilization process. Skeleton-forming proto- 

 bionta have been described mainly in marine sediments. Sporomorpha and 

 spores occur in both marine and limnetic deposits and very exceptionally in 

 terrestrial deposits. Quick embedding in all instances is favorable to the 

 preservation of fossils. Concentration of residues depends upon the following: 

 (1) mass of the organisms; (2) mass of the inorganic material involved in the 

 sedimentation process; {?>) resistance of the organic substance; and (4) destruc- 

 tive factors before and during fossilization (diagenesis). Ciranting factors 1 and 

 v3 even relatively small organisms may affect the mineral composition of rocks, 

 e.g., enrichment of Coccolithophoridae will affect the lime content of marl. 



The rule for concentration of fossil spores or pollen is: 20,000 to 40,000 exines 

 per gram represents the accumulation of normal flora in a given sediment. A 

 larger number per gram is positive proof of autochthonous flora. However, 

 the occurrence of fewer and scattered exines points to contamination. 



Minute fossilia, except for spores and pollen, are found principally in the 

 marine biotope. An aquatic medium is usually necessary for preservation and 

 fossilization of such organisms. 



Theories of extraterrestrial life are based on existing conditions on earth. 

 Each organism, wherever it occurs, must fultill certain regular functions in line 

 with a given physical law in order to remain alive. The most simple organism 



