94 NICHOLS — SPERMATOGENESIS ONISCUS ASELLUS LINN. [April 4 



III. Critical Review of the Literature on Crustacean 

 Spermatogenesis since 1878. 



I. Spermatozoa. 



a. Review. 

 Decapoda. 



1878. Grobben in his valuable work investigates principally the 

 form of the Decapod spermatozoa and their transformations from 

 the immature to the mature state, as well as the nature of the case 

 (spermatophore) in which they are enclosed. With regard to the 

 spermatozoon of Astacus fluviatilis, he states that the head develops 

 from a structure arising near the nucleus, while the nucleus itself 

 disintegrates. He gives also a review of the literature on Crus- 

 tacean spermatozoa up to that time, which therefore need not be 

 repeated here. 



1883 (i). Herrmann describes the spermatozoa of the Podop- 

 thalmia, chiefly the Macrura and Brachyura. The study of the 

 development, he says, shows a series of transitory forms which 

 enable us to seize clearly the bonds of relationship existing between 

 the different adult forms. The transitional forms of some resemble 

 the complete forms of others. 



1884. Nussbaum (Astacus fluviatilis) considers the change of the 

 spermatid into the spermatozoon. He traces the gradual condensa- 

 tion and transformation of the nucleus from spermatid to sper- 

 matozoon, and the transformation of a large body lying in the 

 cytoplasm into the peculiar ''kopfkappe" of the mature sperma- 

 tozoon (see his Figs. 53-68). He regards the nucleus as the head 

 of the spermatozoon. 



1885. Sabatier published a short article on the spermatogenesis 

 of the Decapod Crustacea, principally Astacus. 



1886. Gilson describes the spermatozoa of a considerable num- 

 ber of Decapod species, among others Astacus fluviatilis. The 

 structure of the spermatozoon of the latter he delineates more fully 

 than either of his predecessors. The nucleus he shows to be 

 present and saucer-like in shape. It is covered by a layer of pro- 

 toplasm which is extended laterally into pseudopodic processes. 

 From the centre of the protoplasmic layer sometimes arises a pro- 

 tuberance, to which he gives the name ''globule achromatique.'' 

 The nucleus surmounts a bladder-like vesicle often perforated at the 

 opposite pole. Into this from the centre of the concavity of the 

 nucleus projects what he calls "la tigelle." 



