16 



FUNDAMENTALS OF CYTOLOGY 



great numbers and form large pseudoplasmodia in which the original cell 

 boundaries remain evident (pattern 2), while in another group the uniting 

 cells lose their identity completely and form a true Plasmodium (pattern 

 1). In the anthers of many flowering plants the tapetum is at first a 

 multicellular tissue (pattern 2), but while the microspores complete their 

 development the walls in this tissue disintegrate and allow the protoplasts 

 to flow together as a tapetal Plasmodium (pattern 1). 



Much interest attaches to patterns characterized by continuous cyto- 

 plasm because of the light they shed on the causes of ontogenetic develop- 



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Fig. 8. — Hyaline cartilage from sternum of rabbit. (CuurU^u of General l-iifiaijicdl Supply 



House, Inc., Chicago.) 



ment in organisms with distinct cells. When the condition has arisen as a 

 result of nuclear division without cj^toplasmic division, the resulting body 

 or tissue is best called a coenocyte, whereas such a body or tissue produced 

 by a union of previously distinct cells is known as a syncytium. Evidently 

 there are tissues, such as muscle or connective tissue, that may develop a 

 given pattern in either of these ways. When the mode of development in 

 a tissue under observation is unknown, the nontechnical pattern names 

 used in the foregoing paragraphs should suffice. 



The subdivision and the aggregation of protoplasts are of interest not 

 only from the standpoint of ontogenetic development: their relative 

 importance in the evolution of animals and plants in general has also been 

 a much debated point. The true historical relationship of unicellular and 

 multicellular oi-ganisms is at best uncertain, but that the facts set forth 



