Meaning: The quote you provided is a concise and insightful statement about the fundamental concept of chromosomal inheritance. It was made by Thomas Hunt Morgan, an American evolutionary biologist and geneticist who was awarded the Nobel Prize in Physiology or Medicine in 1933 for his discoveries regarding the role of chromosomes in heredity. Morgan's work laid the foundation for our understanding of genetics and inheritance.

In the quote, Morgan refers to the presence of chromosomes in the eggs and sperm of every species of animal or plant. Chromosomes are thread-like structures located within the nucleus of eukaryotic cells and are composed of DNA and proteins. These chromosomes carry the genetic information of an organism and play a crucial role in the transmission of hereditary traits from one generation to the next.

Morgan emphasizes that the egg of every species contains a specific number of chromosomes, and the same is true for the sperm. When a sperm fertilizes an egg, the resulting fertilized egg, or zygote, contains a double set of chromosomes, combining the genetic material from both the mother and the father. This process, known as fertilization, is essential for the creation of offspring with a unique genetic makeup that contains traits from both parents.

The concept of the double number of chromosomes in the fertilized egg is fundamental to understanding how genetic information is passed from one generation to the next. This doubling of chromosomes ensures genetic diversity and variation within a species, as it allows for the reshuffling and recombination of genetic material during the process of meiosis and sexual reproduction.

Morgan's quote encapsulates the essence of chromosomal inheritance and the significance of the union of egg and sperm in the transmission of genetic information. His research and discoveries paved the way for the modern understanding of genetics, including the identification of specific genes on chromosomes and the mechanisms of inheritance, mutation, and genetic recombination.

Morgan's work with the fruit fly Drosophila melanogaster provided crucial evidence for the chromosome theory of heredity, demonstrating that genes are located on chromosomes and are the units of inheritance. His experiments with Drosophila allowed him to map the location of specific genes on the chromosomes and to observe patterns of inheritance that supported the idea of gene linkage and genetic recombination.

In conclusion, Thomas Hunt Morgan's quote succinctly captures the essence of chromosomal inheritance and the process of fertilization, highlighting the importance of chromosomes in the transmission of genetic information. His pioneering work in genetics laid the groundwork for our modern understanding of heredity and continues to influence the field of genetics and genomics today.