34 LABORATORY DIRECTIONS IN 



soda to destroy the cells inside and to make the gemmules more trans- 

 parent. You should find a small plain or tube-like foraminal aperture 

 through which the small sponge emerges in the spring by an amoeboid 

 movement. 



Using the compound microscope make a drawing of a gemmule an 

 inch in diameter, or show a group of gemmules in a common envelope. 

 Show the foraminal aperture in one of the gemmules. 



3c. Budding in a metazoon (Nais, Aeolosoma, Chaetogaster, Dero, or 

 Microstomum) . When reproduction by budding occurs the elongated 

 body becomes constricted transversely and later separates into two parts. 

 In some cases the worm may show several budding zones. A demonstra- 

 tion will be provided (living if possible) . A sketch in your notes may be 

 helpful, but is not expected on your plates. Be sure to note the name 

 of the worm studied. 



How many parents are concerned in each of the observed cases of 

 asexual reproduction? 



B. Sexual Reproduction 



4. Conjugation in Paramecium. Look in the cultures for paramecia 

 swimming about in pairs side by side. Such specimens are conjugating. 

 The nuclei of conjugating specimens can be studied only with the aid of 

 prepared slides. The essential part of the process is the exchange of 

 portions of the micronuclei. Several demonstrations of this stage will be 

 provided. Draw carefully, representing the body in outline, and the 

 nuclei in detail. Read Chapter VIII in "Principles of Animal Biology," 

 by Shull, La Rue and Ruthven, for an account of conjugation. 



5. Reproduction in an Hermaphroditic Metazoon, the Earthworm. 

 Recall your dissection of the earthworm. Each individual was found to 

 possess both male and female organs. Such an animal is called an 

 hermaphrodite. An earthworm does not, however, fertilize its own eggs; 

 each egg is fertilized by a sperm received from another worm and stored 

 in one of the seminal receptacles (spermathecae) . Make a list of the 

 organs which are classed as female and male and be sure that you know 

 the function of each. 



Examine a demonstration of ova (female germ cells) in the ovary, 

 and also a demonstration of male germ cells in various stages of develop- 

 ment secured from the median seminal vesicles. Read Chapter VIII 

 in " Principles of Animal Biology" for a discussion of reproduction in the 

 earthworm. 



How many parents are concerned in sexual reproduction in each 

 of the cases studied? Were the parents alike or unlike? 



In a majority of species of animals the parents are unlike in structure, 

 each parent having but a single set (male or female) of reproductive organs. 

 Such species are known as dioecious while those which have both sets of 



