384 



Glossary 



bedded in some tissues, and 

 which is produced as a secretion 

 by the cells. It is one kind of 

 intercellular substance. The 

 opalescent, almost homogeneous 

 chief mass of ordinary cartilage 

 is a typical matrix. 



MELANIN. A rather general term 

 in biology, especially in zoology, 

 applied to dark brown to black 

 pigments. 



MEROTOMY. The automatic cutting 

 off of parts or segments in liv- 

 ing organisms. 



MESENCHYME. Undifferentiated 

 mesoderm that produces con- 

 nective tissues, some muscles, 

 and certain other structures in 

 the animal body. 



METABOLIC. Pertaining to metab- 

 olism, the process of chemical 

 building up and breaking down 

 in the living organism. 



METAMERIC. Pertaining to the 

 longitudinal series of parts or 

 joints into which the bodies of 

 many higher animals, such as 

 earthworms, lobsters and fishes, 

 are divided. 



METAPLASTIC. Pertaining to meta- 

 plasm applied to changes which 

 cells sometimes undergo from 

 one plasmic type to another; also 

 applied to certain supposedly 

 lifeless inclusions in the proto- 

 plasm of cells. 



METAZOA. Multicellular animals. 



MICRONUCLEUS. See macronucleus. 



MICHOPHYLE. In botany and zool- 

 ogy the aperture in the coats of 

 the ovule and ovum through 

 which the male fertilizing cell 

 penetrates. 



MONERA. Hypothetical simple 

 structureless masses of proto- 

 plasm (without any nucleus). 

 Assumed by Haeckel as the low- 

 est members of the evolutionary 

 series. Advance of knowledge 

 has found no evidence of such 

 organisms. 



MORPHALLAXIS. A kind of regen- 



eration in which part of an or- 

 ganism transforms directly into 

 a new and different part. 



MORPHOLOGICAL. Pertaining to 

 morphology, the science of form 

 and structure. 



MORULA. A stage in the embryonic 

 development of many animals, in 

 which the ovum has completely 

 segmented, but the segmentation 

 cavity has not yet been formed. 



MYONEME. A thread-like contrac- 

 tile structure in the cytoplasm of 

 certain higher protozoa. 



NEMATOPHORE. A body of defense 

 and offense developed in certain 

 hydroids, consisting of a chitin- 

 ous receptacle in which thread- 

 cells are immersed; the nettling 

 organs on the tentacles of large 

 jelly-fishes. 



NEURAL. Pertaining to nerves. 



NETTHOBLASTS. Undeveloped' nerve 

 cells. 



NUCLEO-PLASM. Nuclear substance, 

 including the different nuclear 

 ingredients. 



NucLEb-pROTEiN. One of the com- 

 pounds of nucleins and paranu- 

 cleins. 



(EDEMA. Dropsy, a vasomotor 

 neurosis characterized by non- 

 inflammatory swellings on vari- 

 ous parts of the body. 



ONTOGENY. The development of an 

 individual organism from germ 

 to completed or adult stage. 



ORGANELLE. A little organ, and 

 organoid, organ-like, are terms 

 applied to the organs of unicel- 

 lular plants and animals, not so 

 much because of their small size 

 and indenniteness of form and 

 structure as on account of the 

 theory that a true organ must 

 be composed of cells, and cannot 

 be a part of a cell. These terms 

 are among the sequelae of the 

 cell-theory. 



ORIENTING. Finding or fixing the 

 positions or directions. 



PANGEN, and PANGENESIS. These 



